a2p
accept
access
acct
addftinfo
addr2line
adjtime
afmtodit
after
aio_cancel
aio_error
aio_read
aio_return
aio_suspend
aio_waitcomplete
aio_write
alias
aliases
alloc
anvil
append
apply
apropos
ar
array
as
asa
asn1parse
at
atq
atrm
attemptckalloc
attemptckrealloc
authlib
authtest
autopoint
awk
b64decode
b64encode
basename
batch
bc
bdes
bell
bg
bgerror
biff
big5
binary
bind
bindkey
bindtags
bindtextdomain
bio
bitmap
blowfish
bn
bootparams
bootptab
bounce
brandelf
break
breaksw
brk
bsdiff
bsdtar
bsnmpd
bspatch
bthost
btsockstat
buffer
builtin
builtins
bunzip2
button
byacc
bzcat
bzegrep
bzfgrep
bzgrep
bzip2
c2ph
c89
c99
ca
cal
calendar
canvas
cap_mkdb
case
cat
catch
catman
cc
cd
cdcontrol
chdir
checkbutton
checknr
chflags
chfn
chgrp
chio
chkey
chmod
chown
chpass
chroot
chsh
ci
ciphers
ckalloc
ckdist
ckfree
ckrealloc
cksum
cleanup
clear
clipboard
clock
clock_getres
clock_gettime
clock_settime
close
cmp
co
col
colcrt
colldef
colors
colrm
column
comm
command
compile_et
complete
compress
concat
config
connect
console
continue
core
courierlogger
couriertcpd
cp
cpan
cpio
cpp
creat
crl
crontab
crunchgen
crunchide
crypt
crypto
csh
csplit
ctags
ctm
ctm_dequeue
ctm_rmail
ctm_smail
cu
cursor
cursors
cut
cvs
date
dbiprof
dbiproxy
dc
dcgettext
dcngettext
dd
dde
default
defer
deliverquota
des
destroy
devfs
df
dgettext
dgst
dh
dhparam
dialog
diff
diff3
dig
dir
dirent
dirname
dirs
discard
disktab
dngettext
do
domainname
done
dprofpp
dsa
dsaparam
dtmfdecode
du
dup
dup2
eaccess
ec
ecdsa
echo
echotc
ecparam
ed
edit
editrc
ee
egrep
elf
elfdump
elif
else
enc
enc2xs
encoding
end
endif
endsw
engine
enigma
entry
env
envsubst
eof
eqn
err
errno
error
errstr
esac
ethers
euc
eui64
eval
event
evp
ex
exec
execve
exit
expand
export
exports
expr
extattr
extattr_delete_fd
extattr_delete_file
extattr_get_fd
extattr_get_file
extattr_set_fd
extattr_set_file
f77
false
famm
famx
fblocked
fbtab
fc
fchdir
fchflags
fchmod
fchown
fcntl
fconfigure
fcopy
fdescfs
fdformat
fdread
fdwrite
fetch
fg
fgrep
fhopen
fhstat
fhstatfs
fi
file
file2c
fileevent
filename
filetest
find
find2perl
finger
flex
flock
flush
fmt
focus
fold
font
fontedit
for
foreach
fork
format
forward
fpathconf
frame
from
fs
fstab
fstat
fstatfs
fsync
ftp
ftpchroot
ftpusers
ftruncate
futimes
g711conv
gb2312
gb18030
gbk
gcc
gcore
gcov
gdb
gencat
gendsa
genrsa
gensnmptree
getconf
getdents
getdirentries
getdtablesize
getegid
geteuid
getfacl
getfh
getfsstat
getgid
getgroups
getitimer
getlogin
getopt
getopts
getpeername
getpgid
getpgrp
getpid
getppid
getpriority
getresgid
getresuid
getrlimit
getrusage
gets
getsid
getsockname
getsockopt
gettext
gettextize
gettimeofday
gettytab
getuid
glob
global
gmake
goto
gperf
gprof
grab
grep
grid
grn
grodvi
groff
groff_font
groff_out
groff_tmac
grog
grolbp
grolj4
grops
grotty
group
groups
gunzip
gzcat
gzexe
gzip
h2ph
h2xs
hash
hashstat
hd
head
help2man
hesinfo
hexdump
history
host
hostname
hosts
hosts_access
hosts_options
hpftodit
http
hup
i386_get_ioperm
i386_get_ldt
i386_set_ioperm
i386_set_ldt
i386_vm86
iconv
id
ident
idprio
if
ifnames253
ifnames259
image
imapd
incr
indent
indxbib
info
infokey
inode
install
instmodsh
interp
intro
introduction
ioctl
ipcrm
ipcs
ipf
ipftest
ipnat
ippool
ipresend
issetugid
jail
jail_attach
jobid
jobs
join
jot
kbdcontrol
kbdmap
kcon
kdestroy
kdump
kenv
kevent
keycap
keylogin
keylogout
keymap
keysyms
kgdb
kill
killall
killpg
kinit
kldfind
kldfirstmod
kldload
kldnext
kldstat
kldsym
kldunload
klist
kpasswd
kqueue
kse
kse_create
kse_exit
kse_release
kse_switchin
kse_thr_interrupt
kse_wakeup
ktrace
label
labelframe
lam
lappend
last
lastcomm
lastlog
lchflags
lchmod
lchown
ld
ldap
ldapadd
ldapcompare
ldapdelete
ldapmodify
ldapmodrdn
ldappasswd
ldapsearch
ldapwhoami
ldd
leave
less
lesskey
lex
lgetfh
lhash
libnetcfg
library
limit
limits
lindex
link
linprocfs
linsert
lint
lio_listio
list
listbox
listen
lj4_font
lkbib
llength
lmtp
ln
load
loadfont
local
locale
locate
lock
lockf
log
logger
login
logins
logname
logout
look
lookbib
lorder
lower
lp
lpq
lpr
lprm
lptest
lrange
lreplace
ls
lsearch
lseek
lset
lsort
lstat
lsvfs
lutimes
lynx
m4
madvise
magic
mail
maildiracl
maildirkw
maildirmake
mailq
mailx
make
makeinfo
makewhatis
man
manpath
master
mc
mcedit
mcview
md2
md4
md5
mdc2
memory
menu
menubar
menubutton
merge
mesg
message
mincore
minherit
minigzip
mkdep
mkdir
mkfifo
mkimapdcert
mklocale
mknod
mkpop3dcert
mkstr
mktemp
mlock
mlockall
mmap
mmroff
modfind
modfnext
modnext
modstat
moduli
more
motd
mount
mprotect
mptable
msdos
msdosfs
msgattrib
msgcat
msgcmp
msgcomm
msgconv
msgen
msgexec
msgfilter
msgfmt
msggrep
msginit
msgmerge
msgs
msgunfmt
msguniq
mskanji
msql2mysql
msync
mt
munlock
munlockall
munmap
mv
myisamchk
myisamlog
myisampack
mysql
mysqlaccess
mysqladmin
mysqlbinlog
mysqlcheck
mysqld
mysqldump
mysqld_multi
mysqld_safe
mysqlhotcopy
mysqlimport
mysqlshow
mysql_config
mysql_fix_privilege_tables
mysql_zap
namespace
nanosleep
nawk
nc
ncal
ncplist
ncplogin
ncplogout
neqn
netconfig
netgroup
netid
netstat
networks
newaliases
newgrp
nex
nfsstat
nfssvc
ngettext
nice
nl
nm
nmount
nohup
nologin
notify
nroff
nseq
nslookup
ntp_adjtime
ntp_gettime
nvi
nview
objcopy
objdump
objformat
ocsp
od
onintr
open
openssl
opieaccess
opieinfo
opiekey
opiekeys
opiepasswd
option
options
oqmgr
pack
package
packagens
pagesize
palette
pam_auth
panedwindow
parray
passwd
paste
patch
pathchk
pathconf
pawd
pax
pbm
pcre
pcreapi
pcrebuild
pcrecallout
pcrecompat
pcrecpp
pcregrep
pcrematching
pcrepartial
pcrepattern
pcreperform
pcreposix
pcreprecompile
pcresample
pcretest
perl
perl56delta
perl58delta
perl561delta
perl570delta
perl571delta
perl572delta
perl573delta
perl581delta
perl582delta
perl583delta
perl584delta
perl585delta
perl586delta
perl587delta
perl588delta
perl5004delta
perl5005delta
perlaix
perlamiga
perlapi
perlapio
perlapollo
perlartistic
perlbeos
perlbook
perlboot
perlbot
perlbs2000
perlbug
perlcall
perlcc
perlce
perlcheat
perlclib
perlcn
perlcompile
perlcygwin
perldata
perldbmfilter
perldebguts
perldebtut
perldebug
perldelta
perldgux
perldiag
perldoc
perldos
perldsc
perlebcdic
perlembed
perlepoc
perlfaq
perlfaq1
perlfaq2
perlfaq3
perlfaq4
perlfaq5
perlfaq6
perlfaq7
perlfaq8
perlfaq9
perlfilter
perlfork
perlform
perlfreebsd
perlfunc
perlglossary
perlgpl
perlguts
perlhack
perlhist
perlhpux
perlhurd
perlintern
perlintro
perliol
perlipc
perlirix
perlivp
perljp
perlko
perllexwarn
perllinux
perllocale
perllol
perlmachten
perlmacos
perlmacosx
perlmint
perlmod
perlmodinstall
perlmodlib
perlmodstyle
perlmpeix
perlnetware
perlnewmod
perlnumber
perlobj
perlop
perlopenbsd
perlopentut
perlos2
perlos390
perlos400
perlothrtut
perlpacktut
perlplan9
perlpod
perlpodspec
perlport
perlqnx
perlre
perlref
perlreftut
perlrequick
perlreref
perlretut
perlrun
perlsec
perlsolaris
perlstyle
perlsub
perlsyn
perlthrtut
perltie
perltoc
perltodo
perltooc
perltoot
perltrap
perltru64
perltw
perlunicode
perluniintro
perlutil
perluts
perlvar
perlvmesa
perlvms
perlvos
perlwin32
perlxs
perlxstut
perror
pfbtops
pftp
pgrep
phones
photo
pic
pickup
piconv
pid
pipe
pkcs7
pkcs8
pkcs12
pkg_add
pkg_check
pkg_create
pkg_delete
pkg_info
pkg_sign
pkg_version
pkill
pl2pm
place
pod2html
pod2latex
pod2man
pod2text
pod2usage
podchecker
podselect
poll
popd
popup
posix_madvise
postalias
postcat
postconf
postdrop
postfix
postkick
postlock
postlog
postmap
postqueue
postsuper
pr
pread
preadv
printcap
printenv
printf
proc
procfs
profil
protocols
prove
proxymap
ps
psed
psroff
pstruct
ptrace
publickey
pushd
puts
pwd
pwrite
pwritev
qmgr
qmqpd
quota
quotactl
radiobutton
raise
rand
ranlib
rcp
rcs
rcsclean
rcsdiff
rcsfile
rcsfreeze
rcsintro
rcsmerge
read
readelf
readlink
readonly
readv
realpath
reboot
recv
recvfrom
recvmsg
red
ree
refer
regexp
registry
regsub
rehash
remote
rename
repeat
replace
req
reset
resolver
resource
return
rev
revoke
rfcomm_sppd
rfork
rhosts
ripemd
ripemd160
rlog
rlogin
rm
rmd160
rmdir
rpc
rpcgen
rs
rsa
rsautl
rsh
rtld
rtprio
rup
ruptime
rusers
rwall
rwho
s2p
safe
sasl
sasldblistusers2
saslpasswd2
sbrk
scache
scale
scan
sched
sched_getparam
sched_getscheduler
sched_get_priority_max
sched_get_priority_min
sched_rr_get_interval
sched_setparam
sched_setscheduler
sched_yield
scon
scp
script
scrollbar
sdiff
sed
seek
select
selection
semctl
semget
semop
send
sendbug
sendfile
sendmail
sendmsg
sendto
services
sess_id
set
setegid
setenv
seteuid
setfacl
setgid
setgroups
setitimer
setlogin
setpgid
setpgrp
setpriority
setregid
setresgid
setresuid
setreuid
setrlimit
setsid
setsockopt
settc
settimeofday
setty
setuid
setvar
sftp
sh
sha
sha1
sha256
shar
shells
shift
shmat
shmctl
shmdt
shmget
showq
shutdown
sigaction
sigaltstack
sigblock
sigmask
sigpause
sigpending
sigprocmask
sigreturn
sigsetmask
sigstack
sigsuspend
sigvec
sigwait
size
slapadd
slapcat
slapd
slapdn
slapindex
slappasswd
slaptest
sleep
slogin
slurpd
smbutil
smime
smtp
smtpd
socket
socketpair
sockstat
soelim
sort
source
spawn
speed
spinbox
spkac
splain
split
squid
squid_ldap_auth
squid_ldap_group
squid_unix_group
sscop
ssh
sshd_config
ssh_config
stab
startslip
stat
statfs
stop
string
strings
strip
stty
su
subst
sum
suspend
swapoff
swapon
switch
symlink
sync
sysarch
syscall
sysconftool
sysconftoolcheck
systat
s_client
s_server
s_time
tabs
tail
talk
tar
tbl
tclsh
tcltest
tclvars
tcopy
tcpdump
tcpslice
tcsh
tee
tell
telltc
telnet
term
termcap
terminfo
test
texindex
texinfo
text
textdomain
tfmtodit
tftp
then
threads
time
tip
tk
tkerror
tkvars
tkwait
tlsmgr
tmac
top
toplevel
touch
tput
tr
trace
trafshow
trap
troff
true
truncate
truss
tset
tsort
tty
ttys
type
tzfile
ui
ul
ulimit
umask
unalias
uname
uncomplete
uncompress
undelete
unexpand
unhash
unifdef
unifdefall
uniq
units
unknown
unlimit
unlink
unmount
unset
unsetenv
until
unvis
update
uplevel
uptime
upvar
usbhidaction
usbhidctl
users
utf8
utimes
utmp
utrace
uudecode
uuencode
uuidgen
vacation
variable
verify
version
vfork
vgrind
vgrindefs
vi
vidcontrol
vidfont
view
virtual
vis
vt220keys
vwait
w
wait
wait3
wait4
waitpid
wall
wc
wget
what
whatis
where
whereis
which
while
who
whoami
whois
window
winfo
wish
wm
write
writev
wtmp
x509
xargs
xgettext
xmlwf
xstr
xsubpp
yacc
yes
ypcat
ypchfn
ypchpass
ypchsh
ypmatch
yppasswd
ypwhich
yyfix
zcat
zcmp
zdiff
zegrep
zfgrep
zforce
zgrep
zmore
znew
_exit
__syscall
 
FreeBSD/Linux/UNIX General Commands Manual
Hypertext Man Pages
perlvar
 
PERLVAR(1)	       Perl Programmers Reference Guide 	    PERLVAR(1)



NAME
       perlvar - Perl predefined variables

DESCRIPTION
       Predefined Names

       The following names have special meaning to Perl.  Most punctuation
       names have reasonable mnemonics, or analogs in the shells.  Neverthe-
       less, if you wish to use long variable names, you need only say

	   use English;

       at the top of your program. This aliases all the short names to the
       long names in the current package. Some even have medium names, gener-
       ally borrowed from awk. In general, it's best to use the

	   use English '-no_match_vars';

       invocation if you don't need $PREMATCH, $MATCH, or $POSTMATCH, as it
       avoids a certain performance hit with the use of regular expressions.
       See English.

       Variables that depend on the currently selected filehandle may be set
       by calling an appropriate object method on the IO::Handle object,
       although this is less efficient than using the regular built-in vari-
       ables. (Summary lines below for this contain the word HANDLE.) First
       you must say

	   use IO::Handle;

       after which you may use either

	   method HANDLE EXPR

       or more safely,

	   HANDLE->method(EXPR)

       Each method returns the old value of the IO::Handle attribute.  The
       methods each take an optional EXPR, which, if supplied, specifies the
       new value for the IO::Handle attribute in question.  If not supplied,
       most methods do nothing to the current value--except for autoflush(),
       which will assume a 1 for you, just to be different.

       Because loading in the IO::Handle class is an expensive operation, you
       should learn how to use the regular built-in variables.

       A few of these variables are considered "read-only".  This means that
       if you try to assign to this variable, either directly or indirectly
       through a reference, you'll raise a run-time exception.

       You should be very careful when modifying the default values of most
       special variables described in this document. In most cases you want to
       localize these variables before changing them, since if you don't, the
       change may affect other modules which rely on the default values of the
       special variables that you have changed. This is one of the correct
       ways to read the whole file at once:

	   open my $fh, "foo" or die $!;
	   local $/; # enable localized slurp mode
	   my $content = <$fh>;
	   close $fh;

       But the following code is quite bad:

	   open my $fh, "foo" or die $!;
	   undef $/; # enable slurp mode
	   my $content = <$fh>;
	   close $fh;

       since some other module, may want to read data from some file in the
       default "line mode", so if the code we have just presented has been
       executed, the global value of $/ is now changed for any other code run-
       ning inside the same Perl interpreter.

       Usually when a variable is localized you want to make sure that this
       change affects the shortest scope possible. So unless you are already
       inside some short "{}" block, you should create one yourself. For exam-
       ple:

	   my $content = '';
	   open my $fh, "foo" or die $!;
	   {
	       local $/;
	       $content = <$fh>;
	   }
	   close $fh;

       Here is an example of how your own code can go broken:

	   for (1..5){
	       nasty_break();
	       print "$_ ";
	   }
	   sub nasty_break {
	       $_ = 5;
	       # do something with $_
	   }

       You probably expect this code to print:

	   1 2 3 4 5

       but instead you get:

	   5 5 5 5 5

       Why? Because nasty_break() modifies $_ without localizing it first. The
       fix is to add local():

	       local $_ = 5;

       It's easy to notice the problem in such a short example, but in more
       complicated code you are looking for trouble if you don't localize
       changes to the special variables.

       The following list is ordered by scalar variables first, then the
       arrays, then the hashes.

       $ARG
       $_      The default input and pattern-searching space.  The following
	       pairs are equivalent:

		   while (<>) {...}    # equivalent only in while!
		   while (defined($_ = <>)) {...}

		   /^Subject:/
		   $_ =~ /^Subject:/

		   tr/a-z/A-Z/
		   $_ =~ tr/a-z/A-Z/

		   chomp
		   chomp($_)

	       Here are the places where Perl will assume $_ even if you don't
	       use it:

	       *  Various unary functions, including functions like ord() and
		  int(), as well as the all file tests ("-f", "-d") except for
		  "-t", which defaults to STDIN.

	       *  Various list functions like print() and unlink().

	       *  The pattern matching operations "m//", "s///", and "tr///"
		  when used without an "=~" operator.

	       *  The default iterator variable in a "foreach" loop if no
		  other variable is supplied.

	       *  The implicit iterator variable in the grep() and map() func-
		  tions.

	       *  The default place to put an input record when a "" oper-
		  ation's result is tested by itself as the sole criterion of
		  a "while" test.  Outside a "while" test, this will not hap-
		  pen.

	       (Mnemonic: underline is understood in certain operations.)

       $a
       $b      Special package variables when using sort(), see "sort" in
	       perlfunc.  Because of this specialness $a and $b don't need to
	       be declared (using use vars, or our()) even when using the
	       "strict 'vars'" pragma.	Don't lexicalize them with "my $a" or
	       "my $b" if you want to be able to use them in the sort() com-
	       parison block or function.

       $<digits>
	       Contains the subpattern from the corresponding set of capturing
	       parentheses from the last pattern match, not counting patterns
	       matched in nested blocks that have been exited already.
	       (Mnemonic: like \digits.)  These variables are all read-only
	       and dynamically scoped to the current BLOCK.

       $MATCH
       $&      The string matched by the last successful pattern match (not
	       counting any matches hidden within a BLOCK or eval() enclosed
	       by the current BLOCK).  (Mnemonic: like & in some editors.)
	       This variable is read-only and dynamically scoped to the cur-
	       rent BLOCK.

	       The use of this variable anywhere in a program imposes a con-
	       siderable performance penalty on all regular expression
	       matches.  See "BUGS".

       $PREMATCH
       $`      The string preceding whatever was matched by the last success-
	       ful pattern match (not counting any matches hidden within a
	       BLOCK or eval enclosed by the current BLOCK).  (Mnemonic: "`"
	       often precedes a quoted string.)  This variable is read-only.

	       The use of this variable anywhere in a program imposes a con-
	       siderable performance penalty on all regular expression
	       matches.  See "BUGS".

       $POSTMATCH
       $'      The string following whatever was matched by the last success-
	       ful pattern match (not counting any matches hidden within a
	       BLOCK or eval() enclosed by the current BLOCK).	(Mnemonic: "'"
	       often follows a quoted string.)	Example:

		   local $_ = 'abcdefghi';
		   /def/;
		   print "$`:$&:$'\n";	       # prints abc:def:ghi

	       This variable is read-only and dynamically scoped to the cur-
	       rent BLOCK.

	       The use of this variable anywhere in a program imposes a con-
	       siderable performance penalty on all regular expression
	       matches.  See "BUGS".

       $LAST_PAREN_MATCH
       $+      The text matched by the last bracket of the last successful
	       search pattern.	This is useful if you don't know which one of
	       a set of alternative patterns matched. For example:

		   /Version: (.*)|Revision: (.*)/ && ($rev = $+);

	       (Mnemonic: be positive and forward looking.)  This variable is
	       read-only and dynamically scoped to the current BLOCK.

       $^N     The text matched by the used group most-recently closed (i.e.
	       the group with the rightmost closing parenthesis) of the last
	       successful search pattern.  (Mnemonic: the (possibly) Nested
	       parenthesis that most recently closed.)

	       This is primarily used inside "(?{...})" blocks for examining
	       text recently matched. For example, to effectively capture text
	       to a variable (in addition to $1, $2, etc.), replace "(...)"
	       with

		    (?:(...)(?{ $var = $^N }))

	       By setting and then using $var in this way relieves you from
	       having to worry about exactly which numbered set of parentheses
	       they are.

	       This variable is dynamically scoped to the current BLOCK.

       @LAST_MATCH_END
       @+      This array holds the offsets of the ends of the last successful
	       submatches in the currently active dynamic scope.  $+[0] is the
	       offset into the string of the end of the entire match.  This is
	       the same value as what the "pos" function returns when called
	       on the variable that was matched against.  The nth element of
	       this array holds the offset of the nth submatch, so $+[1] is
	       the offset past where $1 ends, $+[2] the offset past where $2
	       ends, and so on.  You can use $#+ to determine how many sub-
	       groups were in the last successful match.  See the examples
	       given for the "@-" variable.

       $*      Set to a non-zero integer value to do multi-line matching
	       within a string, 0 (or undefined) to tell Perl that it can
	       assume that strings contain a single line, for the purpose of
	       optimizing pattern matches.  Pattern matches on strings con-
	       taining multiple newlines can produce confusing results when $*
	       is 0 or undefined. Default is undefined.  (Mnemonic: * matches
	       multiple things.) This variable influences the interpretation
	       of only "^" and "$". A literal newline can be searched for even
	       when "$* == 0".

	       Use of $* is deprecated in modern Perl, supplanted by the "/s"
	       and "/m" modifiers on pattern matching.

	       Assigning a non-numerical value to $* triggers a warning (and
	       makes $* act if "$* == 0"), while assigning a numerical value
	       to $* makes that an implicit "int" is applied on the value.

       HANDLE->input_line_number(EXPR)
       $INPUT_LINE_NUMBER
       $NR
       $.      Current line number for the last filehandle accessed.

	       Each filehandle in Perl counts the number of lines that have
	       been read from it.  (Depending on the value of $/, Perl's idea
	       of what constitutes a line may not match yours.)  When a line
	       is read from a filehandle (via readline() or "<>"), or when
	       tell() or seek() is called on it, $. becomes an alias to the
	       line counter for that filehandle.

	       You can adjust the counter by assigning to $., but this will
	       not actually move the seek pointer.  Localizing $. will not
	       localize the filehandle's line count.  Instead, it will local-
	       ize perl's notion of which filehandle $. is currently aliased
	       to.

	       $. is reset when the filehandle is closed, but not when an open
	       filehandle is reopened without an intervening close().  For
	       more details, see "I/O Operators" in perlop.  Because "<>"
	       never does an explicit close, line numbers increase across ARGV
	       files (but see examples in "eof" in perlfunc).

	       You can also use "HANDLE->input_line_number(EXPR)" to access
	       the line counter for a given filehandle without having to worry
	       about which handle you last accessed.

	       (Mnemonic: many programs use "." to mean the current line num-
	       ber.)

       IO::Handle->input_record_separator(EXPR)
       $INPUT_RECORD_SEPARATOR
       $RS
       $/      The input record separator, newline by default.	This influ-
	       ences Perl's idea of what a "line" is.  Works like awk's RS
	       variable, including treating empty lines as a terminator if set
	       to the null string.  (An empty line cannot contain any spaces
	       or tabs.)  You may set it to a multi-character string to match
	       a multi-character terminator, or to "undef" to read through the
	       end of file.  Setting it to "\n\n" means something slightly
	       different than setting to "", if the file contains consecutive
	       empty lines.  Setting to "" will treat two or more consecutive
	       empty lines as a single empty line.  Setting to "\n\n" will
	       blindly assume that the next input character belongs to the
	       next paragraph, even if it's a newline.	(Mnemonic: / delimits
	       line boundaries when quoting poetry.)

		   local $/;	       # enable "slurp" mode
		   local $_ = ;    # whole file now here
		   s/\n[ \t]+/ /g;

	       Remember: the value of $/ is a string, not a regex.  awk has to
	       be better for something. :-)

	       Setting $/ to a reference to an integer, scalar containing an
	       integer, or scalar that's convertible to an integer will
	       attempt to read records instead of lines, with the maximum
	       record size being the referenced integer.  So this:

		   local $/ = \32768; # or \"32768", or \$var_containing_32768
		   open my $fh, $myfile or die $!;
		   local $_ = <$fh>;

	       will read a record of no more than 32768 bytes from FILE.  If
	       you're not reading from a record-oriented file (or your OS
	       doesn't have record-oriented files), then you'll likely get a
	       full chunk of data with every read.  If a record is larger than
	       the record size you've set, you'll get the record back in
	       pieces.

	       On VMS, record reads are done with the equivalent of "sysread",
	       so it's best not to mix record and non-record reads on the same
	       file.  (This is unlikely to be a problem, because any file
	       you'd want to read in record mode is probably unusable in line
	       mode.)  Non-VMS systems do normal I/O, so it's safe to mix
	       record and non-record reads of a file.

	       See also "Newlines" in perlport.  Also see $..

       HANDLE->autoflush(EXPR)
       $OUTPUT_AUTOFLUSH
       $|      If set to nonzero, forces a flush right away and after every
	       write or print on the currently selected output channel.
	       Default is 0 (regardless of whether the channel is really
	       buffered by the system or not; $| tells you only whether you've
	       asked Perl explicitly to flush after each write).  STDOUT will
	       typically be line buffered if output is to the terminal and
	       block buffered otherwise.  Setting this variable is useful pri-
	       marily when you are outputting to a pipe or socket, such as
	       when you are running a Perl program under rsh and want to see
	       the output as it's happening.  This has no effect on input
	       buffering.  See "getc" in perlfunc for that.  (Mnemonic: when
	       you want your pipes to be piping hot.)

       IO::Handle->output_field_separator EXPR
       $OUTPUT_FIELD_SEPARATOR
       $OFS
       $,      The output field separator for the print operator.  If defined,
	       this value is printed between each of print's arguments.
	       Default is "undef".  (Mnemonic: what is printed when there is a
	       "," in your print statement.)

       IO::Handle->output_record_separator EXPR
       $OUTPUT_RECORD_SEPARATOR
       $ORS
       $\      The output record separator for the print operator.  If
	       defined, this value is printed after the last of print's argu-
	       ments.  Default is "undef".  (Mnemonic: you set "$\" instead of
	       adding "\n" at the end of the print.  Also, it's just like $/,
	       but it's what you get "back" from Perl.)

       $LIST_SEPARATOR
       $"      This is like $, except that it applies to array and slice val-
	       ues interpolated into a double-quoted string (or similar inter-
	       preted string).	Default is a space.  (Mnemonic: obvious, I
	       think.)

       $SUBSCRIPT_SEPARATOR
       $SUBSEP
       $;      The subscript separator for multidimensional array emulation.
	       If you refer to a hash element as

		   $foo{$a,$b,$c}

	       it really means

		   $foo{join($;, $a, $b, $c)}

	       But don't put

		   @foo{$a,$b,$c}      # a slice--note the @

	       which means

		   ($foo{$a},$foo{$b},$foo{$c})

	       Default is "\034", the same as SUBSEP in awk.  If your keys
	       contain binary data there might not be any safe value for $;.
	       (Mnemonic: comma (the syntactic subscript separator) is a
	       semi-semicolon.	Yeah, I know, it's pretty lame, but $, is
	       already taken for something more important.)

	       Consider using "real" multidimensional arrays as described in
	       perllol.

       $#      The output format for printed numbers.  This variable is a
	       half-hearted attempt to emulate awk's OFMT variable.  There are
	       times, however, when awk and Perl have differing notions of
	       what counts as numeric.	The initial value is "%.ng", where n
	       is the value of the macro DBL_DIG from your system's float.h.
	       This is different from awk's default OFMT setting of "%.6g", so
	       you need to set $# explicitly to get awk's value.  (Mnemonic: #
	       is the number sign.)

	       Use of $# is deprecated.

       HANDLE->format_page_number(EXPR)
       $FORMAT_PAGE_NUMBER
       $%      The current page number of the currently selected output chan-
	       nel.  Used with formats.  (Mnemonic: % is page number in
	       nroff.)

       HANDLE->format_lines_per_page(EXPR)
       $FORMAT_LINES_PER_PAGE
       $=      The current page length (printable lines) of the currently
	       selected output channel.  Default is 60.  Used with formats.
	       (Mnemonic: = has horizontal lines.)

       HANDLE->format_lines_left(EXPR)
       $FORMAT_LINES_LEFT
       $-      The number of lines left on the page of the currently selected
	       output channel.	Used with formats.  (Mnemonic: lines_on_page -
	       lines_printed.)

       @LAST_MATCH_START
       @-      $-[0] is the offset of the start of the last successful match.
	       "$-["n"]" is the offset of the start of the substring matched
	       by n-th subpattern, or undef if the subpattern did not match.

	       Thus after a match against $_, $& coincides with "substr $_,
	       $-[0], $+[0] - $-[0]".  Similarly, $n coincides with "substr
	       $_, $-[n], $+[n] - $-[n]" if "$-[n]" is defined, and $+ coin-
	       cides with "substr $_, $-[$#-], $+[$#-] - $-[$#-]".  One can
	       use "$#-" to find the last matched subgroup in the last suc-
	       cessful match.  Contrast with $#+, the number of subgroups in
	       the regular expression.	Compare with "@+".

	       This array holds the offsets of the beginnings of the last suc-
	       cessful submatches in the currently active dynamic scope.
	       "$-[0]" is the offset into the string of the beginning of the
	       entire match.  The nth element of this array holds the offset
	       of the nth submatch, so "$-[1]" is the offset where $1 begins,
	       "$-[2]" the offset where $2 begins, and so on.

	       After a match against some variable $var:

	       $` is the same as "substr($var, 0, $-[0])"
	       $& is the same as "substr($var, $-[0], $+[0] - $-[0])"
	       $' is the same as "substr($var, $+[0])"
	       $1 is the same as "substr($var, $-[1], $+[1] - $-[1])"
	       $2 is the same as "substr($var, $-[2], $+[2] - $-[2])"
	       $3 is the same as "substr($var, $-[3], $+[3] - $-[3])"
       HANDLE->format_name(EXPR)
       $FORMAT_NAME
       $~      The name of the current report format for the currently
	       selected output channel.  Default is the name of the filehan-
	       dle.  (Mnemonic: brother to $^.)

       HANDLE->format_top_name(EXPR)
       $FORMAT_TOP_NAME
       $^      The name of the current top-of-page format for the currently
	       selected output channel.  Default is the name of the filehandle
	       with _TOP appended.  (Mnemonic: points to top of page.)

       IO::Handle->format_line_break_characters EXPR
       $FORMAT_LINE_BREAK_CHARACTERS
       $:      The current set of characters after which a string may be bro-
	       ken to fill continuation fields (starting with ^) in a format.
	       Default is " \n-", to break on whitespace or hyphens.
	       (Mnemonic: a "colon" in poetry is a part of a line.)

       IO::Handle->format_formfeed EXPR
       $FORMAT_FORMFEED
       $^L     What formats output as a form feed.  Default is \f.

       $ACCUMULATOR
       $^A     The current value of the write() accumulator for format()
	       lines.  A format contains formline() calls that put their
	       result into $^A.  After calling its format, write() prints out
	       the contents of $^A and empties.  So you never really see the
	       contents of $^A unless you call formline() yourself and then
	       look at it.  See perlform and "formline()" in perlfunc.

       $CHILD_ERROR
       $?      The status returned by the last pipe close, backtick (``) com-
	       mand, successful call to wait() or waitpid(), or from the sys-
	       tem() operator.	This is just the 16-bit status word returned
	       by the wait() system call (or else is made up to look like it).
	       Thus, the exit value of the subprocess is really ("$? >> 8"),
	       and "$? & 127" gives which signal, if any, the process died
	       from, and "$? & 128" reports whether there was a core dump.
	       (Mnemonic: similar to sh and ksh.)

	       Additionally, if the "h_errno" variable is supported in C, its
	       value is returned via $? if any "gethost*()" function fails.

	       If you have installed a signal handler for "SIGCHLD", the value
	       of $? will usually be wrong outside that handler.

	       Inside an "END" subroutine $? contains the value that is going
	       to be given to "exit()".  You can modify $? in an "END" subrou-
	       tine to change the exit status of your program.	For example:

		   END {
		       $? = 1 if $? == 255;  # die would make it 255
		   }

	       Under VMS, the pragma "use vmsish 'status'" makes $? reflect
	       the actual VMS exit status, instead of the default emulation of
	       POSIX status; see "$?" in perlvms for details.

	       Also see "Error Indicators".

       ${^ENCODING}
	       The object reference to the Encode object that is used to con-
	       vert the source code to Unicode.  Thanks to this variable your
	       perl script does not have to be written in UTF-8.  Default is
	       undef.  The direct manipulation of this variable is highly dis-
	       couraged.  See encoding for more details.

       $OS_ERROR
       $ERRNO
       $!      If used numerically, yields the current value of the C "errno"
	       variable, or in other words, if a system or library call fails,
	       it sets this variable.  This means that the value of $! is
	       meaningful only immediately after a failure:

		   if (open(FH, $filename)) {
		       # Here $! is meaningless.
		       ...
		   } else {
		       # ONLY here is $! meaningful.
		       ...
		       # Already here $! might be meaningless.
		   }
		   # Since here we might have either success or failure,
		   # here $! is meaningless.

	       In the above meaningless stands for anything: zero, non-zero,
	       "undef".  A successful system or library call does not set the
	       variable to zero.

	       If used as a string, yields the corresponding system error
	       string.	You can assign a number to $! to set errno if, for
	       instance, you want "$!" to return the string for error n, or
	       you want to set the exit value for the die() operator.
	       (Mnemonic: What just went bang?)

	       Also see "Error Indicators".

       %!      Each element of "%!" has a true value only if $! is set to that
	       value.  For example, $!{ENOENT} is true if and only if the cur-
	       rent value of $! is "ENOENT"; that is, if the most recent error
	       was "No such file or directory" (or its moral equivalent: not
	       all operating systems give that exact error, and certainly not
	       all languages).	To check if a particular key is meaningful on
	       your system, use "exists $!{the_key}"; for a list of legal
	       keys, use "keys %!".  See Errno for more information, and also
	       see above for the validity of $!.

       $EXTENDED_OS_ERROR
       $^E     Error information specific to the current operating system.  At
	       the moment, this differs from $! under only VMS, OS/2, and
	       Win32 (and for MacPerl).  On all other platforms, $^E is always
	       just the same as $!.

	       Under VMS, $^E provides the VMS status value from the last sys-
	       tem error.  This is more specific information about the last
	       system error than that provided by $!.  This is particularly
	       important when $! is set to EVMSERR.

	       Under OS/2, $^E is set to the error code of the last call to
	       OS/2 API either via CRT, or directly from perl.

	       Under Win32, $^E always returns the last error information
	       reported by the Win32 call "GetLastError()" which describes the
	       last error from within the Win32 API.  Most Win32-specific code
	       will report errors via $^E.  ANSI C and Unix-like calls set
	       "errno" and so most portable Perl code will report errors via
	       $!.

	       Caveats mentioned in the description of $! generally apply to
	       $^E, also.  (Mnemonic: Extra error explanation.)

	       Also see "Error Indicators".

       $EVAL_ERROR
       $@      The Perl syntax error message from the last eval() operator.
	       If $@ is the null string, the last eval() parsed and executed
	       correctly (although the operations you invoked may have failed
	       in the normal fashion).	(Mnemonic: Where was the syntax error
	       "at"?)

	       Warning messages are not collected in this variable.  You can,
	       however, set up a routine to process warnings by setting
	       $SIG{__WARN__} as described below.

	       Also see "Error Indicators".

       $PROCESS_ID
       $PID
       $$      The process number of the Perl running this script.  You should
	       consider this variable read-only, although it will be altered
	       across fork() calls.  (Mnemonic: same as shells.)

	       Note for Linux users: on Linux, the C functions "getpid()" and
	       "getppid()" return different values from different threads. In
	       order to be portable, this behavior is not reflected by $$,
	       whose value remains consistent across threads. If you want to
	       call the underlying "getpid()", you may use the CPAN module
	       "Linux::Pid".

       $REAL_USER_ID
       $UID
       $<      The real uid of this process.  (Mnemonic: it's the uid you came
	       from, if you're running setuid.)  You can change both the real
	       uid and the effective uid at the same time by using
	       POSIX::setuid().  Since changes to $< require a system call,
	       check $! after a change attempt to detect any possible errors.

       $EFFECTIVE_USER_ID
       $EUID
       $>      The effective uid of this process.  Example:

		   $< = $>;	       # set real to effective uid
		   ($<,$>) = ($>,$<);  # swap real and effective uid

	       You can change both the effective uid and the real uid at the
	       same time by using POSIX::setuid().  Changes to $> require a
	       check to $!  to detect any possible errors after an attempted
	       change.

	       (Mnemonic: it's the uid you went to, if you're running setuid.)
	       $< and $> can be swapped only on machines supporting
	       setreuid().

       $REAL_GROUP_ID
       $GID
       $(      The real gid of this process.  If you are on a machine that
	       supports membership in multiple groups simultaneously, gives a
	       space separated list of groups you are in.  The first number is
	       the one returned by getgid(), and the subsequent ones by get-
	       groups(), one of which may be the same as the first number.

	       However, a value assigned to $( must be a single number used to
	       set the real gid.  So the value given by $( should not be
	       assigned back to $( without being forced numeric, such as by
	       adding zero.

	       You can change both the real gid and the effective gid at the
	       same time by using POSIX::setgid().  Changes to $( require a
	       check to $!  to detect any possible errors after an attempted
	       change.

	       (Mnemonic: parentheses are used to group things.  The real gid
	       is the group you left, if you're running setgid.)

       $EFFECTIVE_GROUP_ID
       $EGID
       $)      The effective gid of this process.  If you are on a machine
	       that supports membership in multiple groups simultaneously,
	       gives a space separated list of groups you are in.  The first
	       number is the one returned by getegid(), and the subsequent
	       ones by getgroups(), one of which may be the same as the first
	       number.

	       Similarly, a value assigned to $) must also be a space-sepa-
	       rated list of numbers.  The first number sets the effective
	       gid, and the rest (if any) are passed to setgroups().  To get
	       the effect of an empty list for setgroups(), just repeat the
	       new effective gid; that is, to force an effective gid of 5 and
	       an effectively empty setgroups() list, say " $) = "5 5" ".

	       You can change both the effective gid and the real gid at the
	       same time by using POSIX::setgid() (use only a single numeric
	       argument).  Changes to $) require a check to $! to detect any
	       possible errors after an attempted change.

	       (Mnemonic: parentheses are used to group things.  The effective
	       gid is the group that's right for you, if you're running set-
	       gid.)

	       $<, $>, $( and $) can be set only on machines that support the
	       corresponding set[re][ug]id() routine.  $( and $) can be
	       swapped only on machines supporting setregid().

       $PROGRAM_NAME
       $0      Contains the name of the program being executed.

	       On some (read: not all) operating systems assigning to $0 modi-
	       fies the argument area that the "ps" program sees.  On some
	       platforms you may have to use special "ps" options or a differ-
	       ent "ps" to see the changes.  Modifying the $0 is more useful
	       as a way of indicating the current program state than it is for
	       hiding the program you're running.  (Mnemonic: same as sh and
	       ksh.)

	       Note that there are platform specific limitations on the maxi-
	       mum length of $0.  In the most extreme case it may be limited
	       to the space occupied by the original $0.

	       In some platforms there may be arbitrary amount of padding, for
	       example space characters, after the modified name as shown by
	       "ps".  In some platforms this padding may extend all the way to
	       the original length of the argument area, no matter what you do
	       (this is the case for example with Linux 2.2).

	       Note for BSD users: setting $0 does not completely remove
	       "perl" from the ps(1) output.  For example, setting $0 to "foo-
	       bar" may result in "perl: foobar (perl)" (whether both the
	       "perl: " prefix and the " (perl)" suffix are shown depends on
	       your exact BSD variant and version).  This is an operating sys-
	       tem feature, Perl cannot help it.

	       In multithreaded scripts Perl coordinates the threads so that
	       any thread may modify its copy of the $0 and the change becomes
	       visible to ps(1) (assuming the operating system plays along).
	       Note that the view of $0 the other threads have will not change
	       since they have their own copies of it.

       $[      The index of the first element in an array, and of the first
	       character in a substring.  Default is 0, but you could theoret-
	       ically set it to 1 to make Perl behave more like awk (or For-
	       tran) when subscripting and when evaluating the index() and
	       substr() functions.  (Mnemonic: [ begins subscripts.)

	       As of release 5 of Perl, assignment to $[ is treated as a com-
	       piler directive, and cannot influence the behavior of any other
	       file.  (That's why you can only assign compile-time constants
	       to it.)	Its use is highly discouraged.

	       Note that, unlike other compile-time directives (such as
	       strict), assignment to $[ can be seen from outer lexical scopes
	       in the same file.  However, you can use local() on it to
	       strictly bind its value to a lexical block.

       $]      The version + patchlevel / 1000 of the Perl interpreter.  This
	       variable can be used to determine whether the Perl interpreter
	       executing a script is in the right range of versions.
	       (Mnemonic: Is this version of perl in the right bracket?)
	       Example:

		   warn "No checksumming!\n" if $] < 3.019;

	       See also the documentation of "use VERSION" and "require VER-
	       SION" for a convenient way to fail if the running Perl inter-
	       preter is too old.

	       When testing the variable, to steer clear of floating point
	       inaccuracies you might want to prefer the inequality tests "<"
	       and ">" to the tests containing equivalence: "<=", "==", and
	       ">=".

	       The floating point representation can sometimes lead to inaccu-
	       rate numeric comparisons.  See $^V for a more modern represen-
	       tation of the Perl version that allows accurate string compar-
	       isons.

       $COMPILING
       $^C     The current value of the flag associated with the -c switch.
	       Mainly of use with -MO=... to allow code to alter its behavior
	       when being compiled, such as for example to AUTOLOAD at compile
	       time rather than normal, deferred loading.  See perlcc.	Set-
	       ting "$^C = 1" is similar to calling "B::minus_c".

       $DEBUGGING
       $^D     The current value of the debugging flags.  (Mnemonic: value of
	       -D switch.) May be read or set. Like its command-line equiva-
	       lent, you can use numeric or symbolic values, eg "$^D = 10" or
	       "$^D = "st"".

       $SYSTEM_FD_MAX
       $^F     The maximum system file descriptor, ordinarily 2.  System file
	       descriptors are passed to exec()ed processes, while higher file
	       descriptors are not.  Also, during an open(), system file
	       descriptors are preserved even if the open() fails.  (Ordinary
	       file descriptors are closed before the open() is attempted.)
	       The close-on-exec status of a file descriptor will be decided
	       according to the value of $^F when the corresponding file,
	       pipe, or socket was opened, not the time of the exec().

       $^H     WARNING: This variable is strictly for internal use only.  Its
	       availability, behavior, and contents are subject to change
	       without notice.

	       This variable contains compile-time hints for the Perl inter-
	       preter.	At the end of compilation of a BLOCK the value of this
	       variable is restored to the value when the interpreter started
	       to compile the BLOCK.

	       When perl begins to parse any block construct that provides a
	       lexical scope (e.g., eval body, required file, subroutine body,
	       loop body, or conditional block), the existing value of $^H is
	       saved, but its value is left unchanged.	When the compilation
	       of the block is completed, it regains the saved value.  Between
	       the points where its value is saved and restored, code that
	       executes within BEGIN blocks is free to change the value of
	       $^H.

	       This behavior provides the semantic of lexical scoping, and is
	       used in, for instance, the "use strict" pragma.

	       The contents should be an integer; different bits of it are
	       used for different pragmatic flags.  Here's an example:

		   sub add_100 { $^H |= 0x100 }

		   sub foo {
		       BEGIN { add_100() }
		       bar->baz($boon);
		   }

	       Consider what happens during execution of the BEGIN block.  At
	       this point the BEGIN block has already been compiled, but the
	       body of foo() is still being compiled.  The new value of $^H
	       will therefore be visible only while the body of foo() is being
	       compiled.

	       Substitution of the above BEGIN block with:

		   BEGIN { require strict; strict->import('vars') }

	       demonstrates how "use strict 'vars'" is implemented.  Here's a
	       conditional version of the same lexical pragma:

		   BEGIN { require strict; strict->import('vars') if $condition }

       %^H     WARNING: This variable is strictly for internal use only.  Its
	       availability, behavior, and contents are subject to change
	       without notice.

	       The %^H hash provides the same scoping semantic as $^H.	This
	       makes it useful for implementation of lexically scoped pragmas.

       $INPLACE_EDIT
       $^I     The current value of the inplace-edit extension.  Use "undef"
	       to disable inplace editing.  (Mnemonic: value of -i switch.)

       $^M     By default, running out of memory is an untrappable, fatal
	       error.  However, if suitably built, Perl can use the contents
	       of $^M as an emergency memory pool after die()ing.  Suppose
	       that your Perl were compiled with "-DPERL_EMERGENCY_SBRK" and
	       used Perl's malloc.  Then

		   $^M = 'a' x (1 << 16);

	       would allocate a 64K buffer for use in an emergency.  See the
	       INSTALL file in the Perl distribution for information on how to
	       add custom C compilation flags when compiling perl.  To dis-
	       courage casual use of this advanced feature, there is no
	       English long name for this variable.

       $OSNAME
       $^O     The name of the operating system under which this copy of Perl
	       was built, as determined during the configuration process.  The
	       value is identical to $Config{'osname'}.  See also Config and
	       the -V command-line switch documented in perlrun.

	       In Windows platforms, $^O is not very helpful: since it is
	       always "MSWin32", it doesn't tell the difference between
	       95/98/ME/NT/2000/XP/CE/.NET.  Use Win32::GetOSName() or
	       Win32::GetOSVersion() (see Win32 and perlport) to distinguish
	       between the variants.

       ${^OPEN}
	       An internal variable used by PerlIO.  A string in two parts,
	       separated by a "\0" byte, the first part describes the input
	       layers, the second part describes the output layers.

       $PERLDB
       $^P     The internal variable for debugging support.  The meanings of
	       the various bits are subject to change, but currently indicate:

	       0x01  Debug subroutine enter/exit.

	       0x02  Line-by-line debugging.

	       0x04  Switch off optimizations.

	       0x08  Preserve more data for future interactive inspections.

	       0x10  Keep info about source lines on which a subroutine is
		     defined.

	       0x20  Start with single-step on.

	       0x40  Use subroutine address instead of name when reporting.

	       0x80  Report "goto &subroutine" as well.

	       0x100 Provide informative "file" names for evals based on the
		     place they were compiled.

	       0x200 Provide informative names to anonymous subroutines based
		     on the place they were compiled.

	       0x400 Debug assertion subroutines enter/exit.

	       Some bits may be relevant at compile-time only, some at run-
	       time only.  This is a new mechanism and the details may change.

       $LAST_REGEXP_CODE_RESULT
       $^R     The result of evaluation of the last successful "(?{ code })"
	       regular expression assertion (see perlre).  May be written to.

       $EXCEPTIONS_BEING_CAUGHT
       $^S     Current state of the interpreter.

		   $^S	       State
		   ---------   -------------------
		   undef       Parsing module/eval
		   true (1)    Executing an eval
		   false (0)   Otherwise

	       The first state may happen in $SIG{__DIE__} and $SIG{__WARN__}
	       handlers.

       $BASETIME
       $^T     The time at which the program began running, in seconds since
	       the epoch (beginning of 1970).  The values returned by the -M,
	       -A, and -C filetests are based on this value.

       ${^TAINT}
	       Reflects if taint mode is on or off.  1 for on (the program was
	       run with -T), 0 for off, -1 when only taint warnings are
	       enabled (i.e. with -t or -TU).

       ${^UNICODE}
	       Reflects certain Unicode settings of Perl.  See perlrun docu-
	       mentation for the "-C" switch for more information about the
	       possible values. This variable is set during Perl startup and
	       is thereafter read-only.

       ${^UTF8LOCALE}
	       This variable indicates whether an UTF-8 locale was detected by
	       perl at startup. This information is used by perl when it's in
	       adjust-utf8ness-to-locale mode (as when run with the "-CL" com-
	       mand-line switch); see perlrun for more info on this.

       $PERL_VERSION
       $^V     The revision, version, and subversion of the Perl interpreter,
	       represented as a string composed of characters with those ordi-
	       nals.  Thus in Perl v5.6.0 it equals "chr(5) . chr(6) . chr(0)"
	       and will return true for "$^V eq v5.6.0".  Note that the char-
	       acters in this string value can potentially be in Unicode
	       range.

	       This can be used to determine whether the Perl interpreter exe-
	       cuting a script is in the right range of versions.  (Mnemonic:
	       use ^V for Version Control.)  Example:

		   warn "No \"our\" declarations!\n" if $^V and $^V lt v5.6.0;

	       To convert $^V into its string representation use sprintf()'s
	       "%vd" conversion:

		   printf "version is v%vd\n", $^V;  # Perl's version

	       See the documentation of "use VERSION" and "require VERSION"
	       for a convenient way to fail if the running Perl interpreter is
	       too old.

	       See also $] for an older representation of the Perl version.

       $WARNING
       $^W     The current value of the warning switch, initially true if -w
	       was used, false otherwise, but directly modifiable.  (Mnemonic:
	       related to the -w switch.)  See also warnings.

       ${^WARNING_BITS}
	       The current set of warning checks enabled by the "use warnings"
	       pragma.	See the documentation of "warnings" for more details.

       $EXECUTABLE_NAME
       $^X     The name used to execute the current copy of Perl, from C's
	       "argv[0]" or (where supported) /proc/self/exe.

	       Depending on the host operating system, the value of $^X may be
	       a relative or absolute pathname of the perl program file, or
	       may be the string used to invoke perl but not the pathname of
	       the perl program file.  Also, most operating systems permit
	       invoking programs that are not in the PATH environment vari-
	       able, so there is no guarantee that the value of $^X is in
	       PATH.  For VMS, the value may or may not include a version num-
	       ber.

	       You usually can use the value of $^X to re-invoke an indepen-
	       dent copy of the same perl that is currently running, e.g.,

		 @first_run = `$^X -le "print int rand 100 for 1..100"`;

	       But recall that not all operating systems support forking or
	       capturing of the output of commands, so this complex statement
	       may not be portable.

	       It is not safe to use the value of $^X as a path name of a
	       file, as some operating systems that have a mandatory suffix on
	       executable files do not require use of the suffix when invoking
	       a command.  To convert the value of $^X to a path name, use the
	       following statements:

		 # Build up a set of file names (not command names).
		 use Config;
		 $this_perl = $^X;
		 if ($^O ne 'VMS')
		    {$this_perl .= $Config{_exe}
			 unless $this_perl =~ m/$Config{_exe}$/i;}

	       Because many operating systems permit anyone with read access
	       to the Perl program file to make a copy of it, patch the copy,
	       and then execute the copy, the security-conscious Perl program-
	       mer should take care to invoke the installed copy of perl, not
	       the copy referenced by $^X.  The following statements accom-
	       plish this goal, and produce a pathname that can be invoked as
	       a command or referenced as a file.

		 use Config;
		 $secure_perl_path = $Config{perlpath};
		 if ($^O ne 'VMS')
		    {$secure_perl_path .= $Config{_exe}
			 unless $secure_perl_path =~ m/$Config{_exe}$/i;}

       ARGV    The special filehandle that iterates over command-line file-
	       names in @ARGV. Usually written as the null filehandle in the
	       angle operator "<>". Note that currently "ARGV" only has its
	       magical effect within the "<>" operator; elsewhere it is just a
	       plain filehandle corresponding to the last file opened by "<>".
	       In particular, passing "\*ARGV" as a parameter to a function
	       that expects a filehandle may not cause your function to auto-
	       matically read the contents of all the files in @ARGV.

       $ARGV   contains the name of the current file when reading from <>.

       @ARGV   The array @ARGV contains the command-line arguments intended
	       for the script.	$#ARGV is generally the number of arguments
	       minus one, because $ARGV[0] is the first argument, not the pro-
	       gram's command name itself.  See $0 for the command name.

       ARGVOUT The special filehandle that points to the currently open output
	       file when doing edit-in-place processing with -i.  Useful when
	       you have to do a lot of inserting and don't want to keep modi-
	       fying $_.  See perlrun for the -i switch.

       @F      The array @F contains the fields of each line read in when
	       autosplit mode is turned on.  See perlrun for the -a switch.
	       This array is package-specific, and must be declared or given a
	       full package name if not in package main when running under
	       "strict 'vars'".

       @INC    The array @INC contains the list of places that the "do EXPR",
	       "require", or "use" constructs look for their library files.
	       It initially consists of the arguments to any -I command-line
	       switches, followed by the default Perl library, probably
	       /usr/local/lib/perl, followed by ".", to represent the current
	       directory.  ("." will not be appended if taint checks are
	       enabled, either by "-T" or by "-t".)  If you need to modify
	       this at runtime, you should use the "use lib" pragma to get the
	       machine-dependent library properly loaded also:

		   use lib '/mypath/libdir/';
		   use SomeMod;

	       You can also insert hooks into the file inclusion system by
	       putting Perl code directly into @INC.  Those hooks may be sub-
	       routine references, array references or blessed objects.  See
	       "require" in perlfunc for details.

       @_      Within a subroutine the array @_ contains the parameters passed
	       to that subroutine.  See perlsub.

       %INC    The hash %INC contains entries for each filename included via
	       the "do", "require", or "use" operators.  The key is the file-
	       name you specified (with module names converted to pathnames),
	       and the value is the location of the file found.  The "require"
	       operator uses this hash to determine whether a particular file
	       has already been included.

	       If the file was loaded via a hook (e.g. a subroutine reference,
	       see "require" in perlfunc for a description of these hooks),
	       this hook is by default inserted into %INC in place of a file-
	       name.  Note, however, that the hook may have set the %INC entry
	       by itself to provide some more specific info.

       %ENV
       $ENV{expr}
	       The hash %ENV contains your current environment.  Setting a
	       value in "ENV" changes the environment for any child processes
	       you subsequently fork() off.

       %SIG
       $SIG{expr}
	       The hash %SIG contains signal handlers for signals.  For exam-
	       ple:

		   sub handler {       # 1st argument is signal name
		       my($sig) = @_;
		       print "Caught a SIG$sig--shutting down\n";
		       close(LOG);
		       exit(0);
		   }

		   $SIG{'INT'}	= \&handler;
		   $SIG{'QUIT'} = \&handler;
		   ...
		   $SIG{'INT'}	= 'DEFAULT';   # restore default action
		   $SIG{'QUIT'} = 'IGNORE';    # ignore SIGQUIT

	       Using a value of 'IGNORE' usually has the effect of ignoring
	       the signal, except for the "CHLD" signal.  See perlipc for more
	       about this special case.

	       Here are some other examples:

		   $SIG{"PIPE"} = "Plumber";   # assumes main::Plumber (not recommended)
		   $SIG{"PIPE"} = \&Plumber;   # just fine; assume current Plumber
		   $SIG{"PIPE"} = *Plumber;    # somewhat esoteric
		   $SIG{"PIPE"} = Plumber();   # oops, what did Plumber() return??

	       Be sure not to use a bareword as the name of a signal handler,
	       lest you inadvertently call it.

	       If your system has the sigaction() function then signal han-
	       dlers are installed using it.  This means you get reliable sig-
	       nal handling.

	       The default delivery policy of signals changed in Perl 5.8.0
	       from immediate (also known as "unsafe") to deferred, also known
	       as "safe signals".  See perlipc for more information.

	       Certain internal hooks can be also set using the %SIG hash.
	       The routine indicated by $SIG{__WARN__} is called when a warn-
	       ing message is about to be printed.  The warning message is
	       passed as the first argument.  The presence of a __WARN__ hook
	       causes the ordinary printing of warnings to STDERR to be sup-
	       pressed.  You can use this to save warnings in a variable, or
	       turn warnings into fatal errors, like this:

		   local $SIG{__WARN__} = sub { die $_[0] };
		   eval $proggie;

	       The routine indicated by $SIG{__DIE__} is called when a fatal
	       exception is about to be thrown.  The error message is passed
	       as the first argument.  When a __DIE__ hook routine returns,
	       the exception processing continues as it would have in the
	       absence of the hook, unless the hook routine itself exits via a
	       "goto", a loop exit, or a die().  The "__DIE__" handler is
	       explicitly disabled during the call, so that you can die from a
	       "__DIE__" handler.  Similarly for "__WARN__".

	       Due to an implementation glitch, the $SIG{__DIE__} hook is
	       called even inside an eval().  Do not use this to rewrite a
	       pending exception in $@, or as a bizarre substitute for over-
	       riding CORE::GLOBAL::die().  This strange action at a distance
	       may be fixed in a future release so that $SIG{__DIE__} is only
	       called if your program is about to exit, as was the original
	       intent.	Any other use is deprecated.

	       "__DIE__"/"__WARN__" handlers are very special in one respect:
	       they may be called to report (probable) errors found by the
	       parser.	In such a case the parser may be in inconsistent
	       state, so any attempt to evaluate Perl code from such a handler
	       will probably result in a segfault.  This means that warnings
	       or errors that result from parsing Perl should be used with
	       extreme caution, like this:

		   require Carp if defined $^S;
		   Carp::confess("Something wrong") if defined &Carp::confess;
		   die "Something wrong, but could not load Carp to give backtrace...
			To see backtrace try starting Perl with -MCarp switch";

	       Here the first line will load Carp unless it is the parser who
	       called the handler.  The second line will print backtrace and
	       die if Carp was available.  The third line will be executed
	       only if Carp was not available.

	       See "die" in perlfunc, "warn" in perlfunc, "eval" in perlfunc,
	       and warnings for additional information.

       Error Indicators

       The variables $@, $!, $^E, and $? contain information about different
       types of error conditions that may appear during execution of a Perl
       program.  The variables are shown ordered by the "distance" between the
       subsystem which reported the error and the Perl process.  They corre-
       spond to errors detected by the Perl interpreter, C library, operating
       system, or an external program, respectively.

       To illustrate the differences between these variables, consider the
       following Perl expression, which uses a single-quoted string:

	   eval q{
	       open my $pipe, "/cdrom/install |" or die $!;
	       my @res = <$pipe>;
	       close $pipe or die "bad pipe: $?, $!";
	   };

       After execution of this statement all 4 variables may have been set.

       $@ is set if the string to be "eval"-ed did not compile (this may hap-
       pen if "open" or "close" were imported with bad prototypes), or if Perl
       code executed during evaluation die()d .  In these cases the value of
       $@ is the compile error, or the argument to "die" (which will interpo-
       late $! and $?).  (See also Fatal, though.)

       When the eval() expression above is executed, open(), "", and
       "close" are translated to calls in the C run-time library and thence to
       the operating system kernel.  $! is set to the C library's "errno" if
       one of these calls fails.

       Under a few operating systems, $^E may contain a more verbose error
       indicator, such as in this case, "CDROM tray not closed."  Systems that
       do not support extended error messages leave $^E the same as $!.

       Finally, $? may be set to non-0 value if the external program
       /cdrom/install fails.  The upper eight bits reflect specific error con-
       ditions encountered by the program (the program's exit() value).   The
       lower eight bits reflect mode of failure, like signal death and core
       dump information  See wait(2) for details.  In contrast to $! and $^E,
       which are set only if error condition is detected, the variable $? is
       set on each "wait" or pipe "close", overwriting the old value.  This is
       more like $@, which on every eval() is always set on failure and
       cleared on success.

       For more details, see the individual descriptions at $@, $!, $^E, and
       $?.

       Technical Note on the Syntax of Variable Names

       Variable names in Perl can have several formats.  Usually, they must
       begin with a letter or underscore, in which case they can be arbitrar-
       ily long (up to an internal limit of 251 characters) and may contain
       letters, digits, underscores, or the special sequence "::" or "'".  In
       this case, the part before the last "::" or "'" is taken to be a pack-
       age qualifier; see perlmod.

       Perl variable names may also be a sequence of digits or a single punc-
       tuation or control character.  These names are all reserved for special
       uses by Perl; for example, the all-digits names are used to hold data
       captured by backreferences after a regular expression match.  Perl has
       a special syntax for the single-control-character names: It understands
       "^X" (caret "X") to mean the control-"X" character.  For example, the
       notation $^W (dollar-sign caret "W") is the scalar variable whose name
       is the single character control-"W".  This is better than typing a lit-
       eral control-"W" into your program.

       Finally, new in Perl 5.6, Perl variable names may be alphanumeric
       strings that begin with control characters (or better yet, a caret).
       These variables must be written in the form "${^Foo}"; the braces are
       not optional.  "${^Foo}" denotes the scalar variable whose name is a
       control-"F" followed by two "o"'s.  These variables are reserved for
       future special uses by Perl, except for the ones that begin with "^_"
       (control-underscore or caret-underscore).  No control-character name
       that begins with "^_" will acquire a special meaning in any future ver-
       sion of Perl; such names may therefore be used safely in programs.  $^_
       itself, however, is reserved.

       Perl identifiers that begin with digits, control characters, or punctu-
       ation characters are exempt from the effects of the "package" declara-
       tion and are always forced to be in package "main"; they are also
       exempt from "strict 'vars'" errors.  A few other names are also exempt
       in these ways:

	       ENV	       STDIN
	       INC	       STDOUT
	       ARGV	       STDERR
	       ARGVOUT	       _
	       SIG

       In particular, the new special "${^_XYZ}" variables are always taken to
       be in package "main", regardless of any "package" declarations
       presently in scope.

BUGS
       Due to an unfortunate accident of Perl's implementation, "use English"
       imposes a considerable performance penalty on all regular expression
       matches in a program, regardless of whether they occur in the scope of
       "use English".  For that reason, saying "use English" in libraries is
       strongly discouraged.  See the Devel::SawAmpersand module documentation
       from CPAN ( http://www.cpan.org/modules/by-module/Devel/ ) for more
       information.

       Having to even think about the $^S variable in your exception handlers
       is simply wrong.  $SIG{__DIE__} as currently implemented invites griev-
       ous and difficult to track down errors.	Avoid it and use an "END{}" or
       CORE::GLOBAL::die override instead.



perl v5.8.8			  2006-01-07			    PERLVAR(1)
=21105
+2424
(92)