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
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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
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mysqldump
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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
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perlapi
perlapio
perlapollo
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perlbook
perlboot
perlbot
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perlcall
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perlce
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perlclib
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perldbmfilter
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perldebtut
perldebug
perldelta
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perldoc
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perlfaq1
perlfaq2
perlfaq3
perlfaq4
perlfaq5
perlfaq6
perlfaq7
perlfaq8
perlfaq9
perlfilter
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perlfreebsd
perlfunc
perlglossary
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perlmint
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perlmodinstall
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perlopenbsd
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perlutil
perluts
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perlvmesa
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perlwin32
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perlxstut
perror
pfbtops
pftp
pgrep
phones
photo
pic
pickup
piconv
pid
pipe
pkcs7
pkcs8
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pkg_add
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pkg_info
pkg_sign
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pkill
pl2pm
place
pod2html
pod2latex
pod2man
pod2text
pod2usage
podchecker
podselect
poll
popd
popup
posix_madvise
postalias
postcat
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postdrop
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postkick
postlock
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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
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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
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shar
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showq
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slappasswd
slaptest
sleep
slogin
slurpd
smbutil
smime
smtp
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socket
socketpair
sockstat
soelim
sort
source
spawn
speed
spinbox
spkac
splain
split
squid
squid_ldap_auth
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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
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systat
s_client
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tabs
tail
talk
tar
tbl
tclsh
tcltest
tclvars
tcopy
tcpdump
tcpslice
tcsh
tee
tell
telltc
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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
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verify
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vfork
vgrind
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vi
vidcontrol
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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
perldebug
 
PERLDEBUG(1)	       Perl Programmers Reference Guide 	  PERLDEBUG(1)



NAME
       perldebug - Perl debugging

DESCRIPTION
       First of all, have you tried using the -w switch?

       If you're new to the Perl debugger, you may prefer to read perldebtut,
       which is a tutorial introduction to the debugger .

The Perl Debugger
       If you invoke Perl with the -d switch, your script runs under the Perl
       source debugger.  This works like an interactive Perl environment,
       prompting for debugger commands that let you examine source code, set
       breakpoints, get stack backtraces, change the values of variables, etc.
       This is so convenient that you often fire up the debugger all by itself
       just to test out Perl constructs interactively to see what they do.
       For example:

	   $ perl -d -e 42

       In Perl, the debugger is not a separate program the way it usually is
       in the typical compiled environment.  Instead, the -d flag tells the
       compiler to insert source information into the parse trees it's about
       to hand off to the interpreter.	That means your code must first com-
       pile correctly for the debugger to work on it.  Then when the inter-
       preter starts up, it preloads a special Perl library file containing
       the debugger.

       The program will halt right before the first run-time executable state-
       ment (but see below regarding compile-time statements) and ask you to
       enter a debugger command.  Contrary to popular expectations, whenever
       the debugger halts and shows you a line of code, it always displays the
       line it's about to execute, rather than the one it has just executed.

       Any command not recognized by the debugger is directly executed
       ("eval"'d) as Perl code in the current package.	(The debugger uses the
       DB package for keeping its own state information.)

       Note that the said "eval" is bound by an implicit scope. As a result
       any newly introduced lexical variable or any modified capture buffer
       content is lost after the eval. The debugger is a nice environment to
       learn Perl, but if you interactively experiment using material which
       should be in the same scope, stuff it in one line.

       For any text entered at the debugger prompt, leading and trailing
       whitespace is first stripped before further processing.	If a debugger
       command coincides with some function in your own program, merely pre-
       cede the function with something that doesn't look like a debugger com-
       mand, such as a leading ";" or perhaps a "+", or by wrapping it with
       parentheses or braces.

       Debugger Commands

       The debugger understands the following commands:

       h	   Prints out a summary help message

       h [command] Prints out a help message for the given debugger command.

       h h	   The special argument of "h h" produces the entire help
		   page, which is quite long.

		   If the output of the "h h" command (or any command, for
		   that matter) scrolls past your screen, precede the command
		   with a leading pipe symbol so that it's run through your
		   pager, as in

		       DB> |h h

		   You may change the pager which is used via "o pager=..."
		   command.

       p expr	   Same as "print {$DB::OUT} expr" in the current package.  In
		   particular, because this is just Perl's own "print" func-
		   tion, this means that nested data structures and objects
		   are not dumped, unlike with the "x" command.

		   The "DB::OUT" filehandle is opened to /dev/tty, regardless
		   of where STDOUT may be redirected to.

       x [maxdepth] expr
		   Evaluates its expression in list context and dumps out the
		   result in a pretty-printed fashion.	Nested data structures
		   are printed out recursively, unlike the real "print" func-
		   tion in Perl.  When dumping hashes, you'll probably prefer
		   'x \%h' rather than 'x %h'.	See Dumpvalue if you'd like to
		   do this yourself.

		   The output format is governed by multiple options described
		   under "Configurable Options".

		   If the "maxdepth" is included, it must be a numeral N; the
		   value is dumped only N levels deep, as if the "dumpDepth"
		   option had been temporarily set to N.

       V [pkg [vars]]
		   Display all (or some) variables in package (defaulting to
		   "main") using a data pretty-printer (hashes show their keys
		   and values so you see what's what, control characters are
		   made printable, etc.).  Make sure you don't put the type
		   specifier (like "$") there, just the symbol names, like
		   this:

		       V DB filename line

		   Use "~pattern" and "!pattern" for positive and negative
		   regexes.

		   This is similar to calling the "x" command on each applica-
		   ble var.

       X [vars]    Same as "V currentpackage [vars]".

       y [level [vars]]
		   Display all (or some) lexical variables (mnemonic: "mY"
		   variables) in the current scope or level scopes higher.
		   You can limit the variables that you see with vars which
		   works exactly as it does for the "V" and "X" commands.
		   Requires the "PadWalker" module version 0.08 or higher;
		   will warn if this isn't installed.  Output is pretty-
		   printed in the same style as for "V" and the format is con-
		   trolled by the same options.

       T	   Produce a stack backtrace.  See below for details on its
		   output.

       s [expr]    Single step.  Executes until the beginning of another
		   statement, descending into subroutine calls.  If an expres-
		   sion is supplied that includes function calls, it too will
		   be single-stepped.

       n [expr]    Next.  Executes over subroutine calls, until the beginning
		   of the next statement.  If an expression is supplied that
		   includes function calls, those functions will be executed
		   with stops before each statement.

       r	   Continue until the return from the current subroutine.
		   Dump the return value if the "PrintRet" option is set
		   (default).

       	   Repeat last "n" or "s" command.

       c [line|sub]
		   Continue, optionally inserting a one-time-only breakpoint
		   at the specified line or subroutine.

       l	   List next window of lines.

       l min+incr  List "incr+1" lines starting at "min".

       l min-max   List lines "min" through "max".  "l -" is synonymous to
		   "-".

       l line	   List a single line.

       l subname   List first window of lines from subroutine.	subname may be
		   a variable that contains a code reference.

       -	   List previous window of lines.

       v [line]    View a few lines of code around the current line.

       .	   Return the internal debugger pointer to the line last exe-
		   cuted, and print out that line.

       f filename  Switch to viewing a different file or "eval" statement.  If
		   filename is not a full pathname found in the values of
		   %INC, it is considered a regex.

		   "eval"ed strings (when accessible) are considered to be
		   filenames: "f (eval 7)" and "f eval 7\b" access the body of
		   the 7th "eval"ed string (in the order of execution).  The
		   bodies of the currently executed "eval" and of "eval"ed
		   strings that define subroutines are saved and thus accessi-
		   ble.

       /pattern/   Search forwards for pattern (a Perl regex); final / is
		   optional.  The search is case-insensitive by default.

       ?pattern?   Search backwards for pattern; final ? is optional.  The
		   search is case-insensitive by default.

       L [abw]	   List (default all) actions, breakpoints and watch expres-
		   sions

       S [[!]regex]
		   List subroutine names [not] matching the regex.

       t	   Toggle trace mode (see also the "AutoTrace" option).

       t expr	   Trace through execution of "expr".  See "Frame Listing Out-
		   put Examples" in perldebguts for examples.

       b	   Sets breakpoint on current line

       b [line] [condition]
		   Set a breakpoint before the given line.  If a condition is
		   specified, it's evaluated each time the statement is
		   reached: a breakpoint is taken only if the condition is
		   true.  Breakpoints may only be set on lines that begin an
		   executable statement.  Conditions don't use "if":

		       b 237 $x > 30
		       b 237 ++$count237 < 11
		       b 33 /pattern/i

       b subname [condition]
		   Set a breakpoint before the first line of the named subrou-
		   tine.  subname may be a variable containing a code refer-
		   ence (in this case condition is not supported).

       b postpone subname [condition]
		   Set a breakpoint at first line of subroutine after it is
		   compiled.

       b load filename
		   Set a breakpoint before the first executed line of the
		   filename, which should be a full pathname found amongst the
		   %INC values.

       b compile subname
		   Sets a breakpoint before the first statement executed after
		   the specified subroutine is compiled.

       B line	   Delete a breakpoint from the specified line.

       B *	   Delete all installed breakpoints.

       a [line] command
		   Set an action to be done before the line is executed.  If
		   line is omitted, set an action on the line about to be exe-
		   cuted.  The sequence of steps taken by the debugger is

		     1. check for a breakpoint at this line
		     2. print the line if necessary (tracing)
		     3. do any actions associated with that line
		     4. prompt user if at a breakpoint or in single-step
		     5. evaluate line

		   For example, this will print out $foo every time line 53 is
		   passed:

		       a 53 print "DB FOUND $foo\n"

       A line	   Delete an action from the specified line.

       A *	   Delete all installed actions.

       w expr	   Add a global watch-expression.  We hope you know what one
		   of these is, because they're supposed to be obvious.

       W expr	   Delete watch-expression

       W *	   Delete all watch-expressions.

       o	   Display all options

       o booloption ...
		   Set each listed Boolean option to the value 1.

       o anyoption? ...
		   Print out the value of one or more options.

       o option=value ...
		   Set the value of one or more options.  If the value has
		   internal whitespace, it should be quoted.  For example, you
		   could set "o pager="less -MQeicsNfr"" to call less with
		   those specific options.  You may use either single or dou-
		   ble quotes, but if you do, you must escape any embedded
		   instances of same sort of quote you began with, as well as
		   any escaping any escapes that immediately precede that
		   quote but which are not meant to escape the quote itself.
		   In other words, you follow single-quoting rules irrespec-
		   tive of the quote; eg: "o option='this isn\'t bad'" or "o
		   option="She said, \"Isn't it?\""".

		   For historical reasons, the "=value" is optional, but
		   defaults to 1 only where it is safe to do so--that is,
		   mostly for Boolean options.	It is always better to assign
		   a specific value using "=".	The "option" can be abbrevi-
		   ated, but for clarity probably should not be.  Several
		   options can be set together.  See "Configurable Options"
		   for a list of these.

       < ?	   List out all pre-prompt Perl command actions.

       < [ command ]
		   Set an action (Perl command) to happen before every debug-
		   ger prompt.	A multi-line command may be entered by back-
		   slashing the newlines.

       < *	   Delete all pre-prompt Perl command actions.

       << command  Add an action (Perl command) to happen before every debug-
		   ger prompt.	A multi-line command may be entered by back-
		   whacking the newlines.

       > ?	   List out post-prompt Perl command actions.

       > command   Set an action (Perl command) to happen after the prompt
		   when you've just given a command to return to executing the
		   script.  A multi-line command may be entered by backslash-
		   ing the newlines (we bet you couldn't've guessed this by
		   now).

       > *	   Delete all post-prompt Perl command actions.

       >> command  Adds an action (Perl command) to happen after the prompt
		   when you've just given a command to return to executing the
		   script.  A multi-line command may be entered by backslash-
		   ing the newlines.

       { ?	   List out pre-prompt debugger commands.

       { [ command ]
		   Set an action (debugger command) to happen before every
		   debugger prompt.  A multi-line command may be entered in
		   the customary fashion.

		   Because this command is in some senses new, a warning is
		   issued if you appear to have accidentally entered a block
		   instead.  If that's what you mean to do, write it as with
		   ";{ ... }" or even "do { ... }".

       { *	   Delete all pre-prompt debugger commands.

       {{ command  Add an action (debugger command) to happen before every
		   debugger prompt.  A multi-line command may be entered, if
		   you can guess how: see above.

       ! number    Redo a previous command (defaults to the previous command).

       ! -number   Redo number'th previous command.

       ! pattern   Redo last command that started with pattern.  See "o
		   recallCommand", too.

       !! cmd	   Run cmd in a subprocess (reads from DB::IN, writes to
		   DB::OUT) See "o shellBang", also.  Note that the user's
		   current shell (well, their $ENV{SHELL} variable) will be
		   used, which can interfere with proper interpretation of
		   exit status or signal and coredump information.

       source file Read and execute debugger commands from file.  file may
		   itself contain "source" commands.

       H -number   Display last n commands.  Only commands longer than one
		   character are listed.  If number is omitted, list them all.

       q or ^D	   Quit.  ("quit" doesn't work for this, unless you've made an
		   alias) This is the only supported way to exit the debugger,
		   though typing "exit" twice might work.

		   Set the "inhibit_exit" option to 0 if you want to be able
		   to step off the end the script.  You may also need to set
		   $finished to 0 if you want to step through global destruc-
		   tion.

       R	   Restart the debugger by "exec()"ing a new session.  We try
		   to maintain your history across this, but internal settings
		   and command-line options may be lost.

		   The following setting are currently preserved: history,
		   breakpoints, actions, debugger options, and the Perl com-
		   mand-line options -w, -I, and -e.

       |dbcmd	   Run the debugger command, piping DB::OUT into your current
		   pager.

       ||dbcmd	   Same as "|dbcmd" but DB::OUT is temporarily "select"ed as
		   well.

       = [alias value]
		   Define a command alias, like

		       = quit q

		   or list current aliases.

       command	   Execute command as a Perl statement.  A trailing semicolon
		   will be supplied.  If the Perl statement would otherwise be
		   confused for a Perl debugger, use a leading semicolon, too.

       m expr	   List which methods may be called on the result of the eval-
		   uated expression.  The expression may evaluated to a refer-
		   ence to a blessed object, or to a package name.

       M	   Displays all loaded modules and their versions

       man [manpage]
		   Despite its name, this calls your system's default documen-
		   tation viewer on the given page, or on the viewer itself if
		   manpage is omitted.	If that viewer is man, the current
		   "Config" information is used to invoke man using the proper
		   MANPATH or -M manpath option.  Failed lookups of the form
		   "XXX" that match known manpages of the form perlXXX will be
		   retried.  This lets you type "man debug" or "man op" from
		   the debugger.

		   On systems traditionally bereft of a usable man command,
		   the debugger invokes perldoc.  Occasionally this determina-
		   tion is incorrect due to recalcitrant vendors or rather
		   more felicitously, to enterprising users.  If you fall into
		   either category, just manually set the $DB::doccmd variable
		   to whatever viewer to view the Perl documentation on your
		   system.  This may be set in an rc file, or through direct
		   assignment.	We're still waiting for a working example of
		   something along the lines of:

		       $DB::doccmd = 'netscape -remote http://something.here/';

       Configurable Options

       The debugger has numerous options settable using the "o" command,
       either interactively or from the environment or an rc file.  (./.perldb
       or ~/.perldb under Unix.)

       "recallCommand", "ShellBang"
		   The characters used to recall command or spawn shell.  By
		   default, both are set to "!", which is unfortunate.

       "pager"	   Program to use for output of pager-piped commands (those
		   beginning with a "|" character.)  By default, $ENV{PAGER}
		   will be used.  Because the debugger uses your current ter-
		   minal characteristics for bold and underlining, if the cho-
		   sen pager does not pass escape sequences through unchanged,
		   the output of some debugger commands will not be readable
		   when sent through the pager.

       "tkRunning" Run Tk while prompting (with ReadLine).

       "signalLevel", "warnLevel", "dieLevel"
		   Level of verbosity.	By default, the debugger leaves your
		   exceptions and warnings alone, because altering them can
		   break correctly running programs.  It will attempt to print
		   a message when uncaught INT, BUS, or SEGV signals arrive.
		   (But see the mention of signals in BUGS below.)

		   To disable this default safe mode, set these values to
		   something higher than 0.  At a level of 1, you get back-
		   traces upon receiving any kind of warning (this is often
		   annoying) or exception (this is often valuable).  Unfortu-
		   nately, the debugger cannot discern fatal exceptions from
		   non-fatal ones.  If "dieLevel" is even 1, then your non-
		   fatal exceptions are also traced and unceremoniously
		   altered if they came from "eval'd" strings or from any kind
		   of "eval" within modules you're attempting to load.	If
		   "dieLevel" is 2, the debugger doesn't care where they came
		   from:  It usurps your exception handler and prints out a
		   trace, then modifies all exceptions with its own embellish-
		   ments.  This may perhaps be useful for some tracing pur-
		   poses, but tends to hopelessly destroy any program that
		   takes its exception handling seriously.

       "AutoTrace" Trace mode (similar to "t" command, but can be put into
		   "PERLDB_OPTS").

       "LineInfo"  File or pipe to print line number info to.  If it is a pipe
		   (say, "|visual_perl_db"), then a short message is used.
		   This is the mechanism used to interact with a slave editor
		   or visual debugger, such as the special "vi" or "emacs"
		   hooks, or the "ddd" graphical debugger.

       "inhibit_exit"
		   If 0, allows stepping off the end of the script.

       "PrintRet"  Print return value after "r" command if set (default).

       "ornaments" Affects screen appearance of the command line (see
		   Term::ReadLine).  There is currently no way to disable
		   these, which can render some output illegible on some dis-
		   plays, or with some pagers.	This is considered a bug.

       "frame"	   Affects the printing of messages upon entry and exit from
		   subroutines.  If "frame & 2" is false, messages are printed
		   on entry only. (Printing on exit might be useful if inter-
		   spersed with other messages.)

		   If "frame & 4", arguments to functions are printed, plus
		   context and caller info.  If "frame & 8", overloaded
		   "stringify" and "tie"d "FETCH" is enabled on the printed
		   arguments.  If "frame & 16", the return value from the sub-
		   routine is printed.

		   The length at which the argument list is truncated is gov-
		   erned by the next option:

       "maxTraceLen"
		   Length to truncate the argument list when the "frame"
		   option's bit 4 is set.

       "windowSize"
		   Change the size of code list window (default is 10 lines).

       The following options affect what happens with "V", "X", and "x" com-
       mands:

       "arrayDepth", "hashDepth"
		   Print only first N elements ('' for all).

       "dumpDepth" Limit recursion depth to N levels when dumping structures.
		   Negative values are interpreted as infinity.  Default:
		   infinity.

       "compactDump", "veryCompact"
		   Change the style of array and hash output.  If "compact-
		   Dump", short array may be printed on one line.

       "globPrint" Whether to print contents of globs.

       "DumpDBFiles"
		   Dump arrays holding debugged files.

       "DumpPackages"
		   Dump symbol tables of packages.

       "DumpReused"
		   Dump contents of "reused" addresses.

       "quote", "HighBit", "undefPrint"
		   Change the style of string dump.  The default value for
		   "quote" is "auto"; one can enable double-quotish or single-
		   quotish format by setting it to """ or "'", respectively.
		   By default, characters with their high bit set are printed
		   verbatim.

       "UsageOnly" Rudimentary per-package memory usage dump.  Calculates
		   total size of strings found in variables in the package.
		   This does not include lexicals in a module's file scope, or
		   lost in closures.

       After the rc file is read, the debugger reads the $ENV{PERLDB_OPTS}
       environment variable and parses this as the remainder of a "O ..."
       line as one might enter at the debugger prompt.	You may place the ini-
       tialization options "TTY", "noTTY", "ReadLine", and "NonStop" there.

       If your rc file contains:

	 parse_options("NonStop=1 LineInfo=db.out AutoTrace");

       then your script will run without human intervention, putting trace
       information into the file db.out.  (If you interrupt it, you'd better
       reset "LineInfo" to /dev/tty if you expect to see anything.)

       "TTY"	   The TTY to use for debugging I/O.

       "noTTY"	   If set, the debugger goes into "NonStop" mode and will not
		   connect to a TTY.  If interrupted (or if control goes to
		   the debugger via explicit setting of $DB::signal or
		   $DB::single from the Perl script), it connects to a TTY
		   specified in the "TTY" option at startup, or to a tty found
		   at runtime using the "Term::Rendezvous" module of your
		   choice.

		   This module should implement a method named "new" that
		   returns an object with two methods: "IN" and "OUT".	These
		   should return filehandles to use for debugging input and
		   output correspondingly.  The "new" method should inspect an
		   argument containing the value of $ENV{PERLDB_NOTTY} at
		   startup, or "$ENV{HOME}/.perldbtty$$" otherwise.  This file
		   is not inspected for proper ownership, so security hazards
		   are theoretically possible.

       "ReadLine"  If false, readline support in the debugger is disabled in
		   order to debug applications that themselves use ReadLine.

       "NonStop"   If set, the debugger goes into non-interactive mode until
		   interrupted, or programmatically by setting $DB::signal or
		   $DB::single.

       Here's an example of using the $ENV{PERLDB_OPTS} variable:

	   $ PERLDB_OPTS="NonStop frame=2" perl -d myprogram

       That will run the script myprogram without human intervention, printing
       out the call tree with entry and exit points.  Note that "NonStop=1
       frame=2" is equivalent to "N f=2", and that originally, options could
       be uniquely abbreviated by the first letter (modulo the "Dump*"
       options).  It is nevertheless recommended that you always spell them
       out in full for legibility and future compatibility.

       Other examples include

	   $ PERLDB_OPTS="NonStop LineInfo=listing frame=2" perl -d myprogram

       which runs script non-interactively, printing info on each entry into a
       subroutine and each executed line into the file named listing.  (If you
       interrupt it, you would better reset "LineInfo" to something "interac-
       tive"!)

       Other examples include (using standard shell syntax to show environment
       variable settings):

	 $ ( PERLDB_OPTS="NonStop frame=1 AutoTrace LineInfo=tperl.out"
	     perl -d myprogram )

       which may be useful for debugging a program that uses "Term::ReadLine"
       itself.	Do not forget to detach your shell from the TTY in the window
       that corresponds to /dev/ttyXX, say, by issuing a command like

	 $ sleep 1000000

       See "Debugger Internals" in perldebguts for details.

       Debugger input/output


       Prompt  The debugger prompt is something like

		   DB<8>

	       or even

		   DB<<17>>

	       where that number is the command number, and which you'd use to
	       access with the built-in csh-like history mechanism.  For exam-
	       ple, "!17" would repeat command number 17.  The depth of the
	       angle brackets indicates the nesting depth of the debugger.
	       You could get more than one set of brackets, for example, if
	       you'd already at a breakpoint and then printed the result of a
	       function call that itself has a breakpoint, or you step into an
	       expression via "s/n/t expression" command.

       Multiline commands
	       If you want to enter a multi-line command, such as a subroutine
	       definition with several statements or a format, escape the new-
	       line that would normally end the debugger command with a back-
	       slash.  Here's an example:

		     DB<1> for (1..4) { 	\
		     cont:     print "ok\n";   \
		     cont: }
		     ok
		     ok
		     ok
		     ok

	       Note that this business of escaping a newline is specific to
	       interactive commands typed into the debugger.

       Stack backtrace
	       Here's an example of what a stack backtrace via "T" command
	       might look like:

		   $ = main::infested called from file `Ambulation.pm' line 10
		   @ = Ambulation::legs(1, 2, 3, 4) called from file `camel_flea' line 7
		   $ = main::pests('bactrian', 4) called from file `camel_flea' line 4

	       The left-hand character up there indicates the context in which
	       the function was called, with "$" and "@" meaning scalar or
	       list contexts respectively, and "." meaning void context (which
	       is actually a sort of scalar context).  The display above says
	       that you were in the function "main::infested" when you ran the
	       stack dump, and that it was called in scalar context from line
	       10 of the file Ambulation.pm, but without any arguments at all,
	       meaning it was called as &infested.  The next stack frame shows
	       that the function "Ambulation::legs" was called in list context
	       from the camel_flea file with four arguments.  The last stack
	       frame shows that "main::pests" was called in scalar context,
	       also from camel_flea, but from line 4.

	       If you execute the "T" command from inside an active "use"
	       statement, the backtrace will contain both a "require" frame
	       and an "eval") frame.

       Line Listing Format
	       This shows the sorts of output the "l" command can produce:

		   DB<<13>> l
		 101:		     @i{@i} = ();
		 102:b		     @isa{@i,$pack} = ()
		 103			 if(exists $i{$prevpack} || exists $isa{$pack});
		 104		 }
		 105
		 106		 next
		 107==> 	     if(exists $isa{$pack});
		 108
		 109:a		 if ($extra-- > 0) {
		 110:		     %isa = ($pack,1);

	       Breakable lines are marked with ":".  Lines with breakpoints
	       are marked by "b" and those with actions by "a".  The line
	       that's about to be executed is marked by "==>".

	       Please be aware that code in debugger listings may not look the
	       same as your original source code.  Line directives and exter-
	       nal source filters can alter the code before Perl sees it,
	       causing code to move from its original positions or take on
	       entirely different forms.

       Frame listing
	       When the "frame" option is set, the debugger would print
	       entered (and optionally exited) subroutines in different
	       styles.	See perldebguts for incredibly long examples of these.

       Debugging compile-time statements

       If you have compile-time executable statements (such as code within
       BEGIN and CHECK blocks or "use" statements), these will not be stopped
       by debugger, although "require"s and INIT blocks will, and compile-time
       statements can be traced with "AutoTrace" option set in "PERLDB_OPTS").
       From your own Perl code, however, you can transfer control back to the
       debugger using the following statement, which is harmless if the debug-
       ger is not running:

	   $DB::single = 1;

       If you set $DB::single to 2, it's equivalent to having just typed the
       "n" command, whereas a value of 1 means the "s" command.  The
       $DB::trace  variable should be set to 1 to simulate having typed the
       "t" command.

       Another way to debug compile-time code is to start the debugger, set a
       breakpoint on the load of some module:

	   DB<7> b load f:/perllib/lib/Carp.pm
	 Will stop on load of `f:/perllib/lib/Carp.pm'.

       and then restart the debugger using the "R" command (if possible).  One
       can use "b compile subname" for the same purpose.

       Debugger Customization

       The debugger probably contains enough configuration hooks that you
       won't ever have to modify it yourself.  You may change the behaviour of
       debugger from within the debugger using its "o" command, from the com-
       mand line via the "PERLDB_OPTS" environment variable, and from cus-
       tomization files.

       You can do some customization by setting up a .perldb file, which con-
       tains initialization code.  For instance, you could make aliases like
       these (the last one is one people expect to be there):

	   $DB::alias{'len'}  = 's/^len(.*)/p length($1)/';
	   $DB::alias{'stop'} = 's/^stop (at|in)/b/';
	   $DB::alias{'ps'}   = 's/^ps\b/p scalar /';
	   $DB::alias{'quit'} = 's/^quit(\s*)/exit/';

       You can change options from .perldb by using calls like this one;

	   parse_options("NonStop=1 LineInfo=db.out AutoTrace=1 frame=2");

       The code is executed in the package "DB".  Note that .perldb is pro-
       cessed before processing "PERLDB_OPTS".	If .perldb defines the subrou-
       tine "afterinit", that function is called after debugger initialization
       ends.  .perldb may be contained in the current directory, or in the
       home directory.	Because this file is sourced in by Perl and may con-
       tain arbitrary commands, for security reasons, it must be owned by the
       superuser or the current user, and writable by no one but its owner.

       You can mock TTY input to debugger by adding arbitrary commands to
       @DB::typeahead. For example, your .perldb file might contain:

	   sub afterinit { push @DB::typeahead, "b 4", "b 6"; }

       Which would attempt to set breakpoints on lines 4 and 6 immediately
       after debugger initialization. Note that @DB::typeahead is not a sup-
       ported interface and is subject to change in future releases.

       If you want to modify the debugger, copy perl5db.pl from the Perl
       library to another name and hack it to your heart's content.  You'll
       then want to set your "PERL5DB" environment variable to say something
       like this:

	   BEGIN { require "myperl5db.pl" }

       As a last resort, you could also use "PERL5DB" to customize the debug-
       ger by directly setting internal variables or calling debugger func-
       tions.

       Note that any variables and functions that are not documented in this
       document (or in perldebguts) are considered for internal use only, and
       as such are subject to change without notice.

       Readline Support

       As shipped, the only command-line history supplied is a simplistic one
       that checks for leading exclamation points.  However, if you install
       the Term::ReadKey and Term::ReadLine modules from CPAN, you will have
       full editing capabilities much like GNU readline(3) provides.  Look for
       these in the modules/by-module/Term directory on CPAN.  These do not
       support normal vi command-line editing, however.

       A rudimentary command-line completion is also available.  Unfortu-
       nately, the names of lexical variables are not available for comple-
       tion.

       Editor Support for Debugging

       If you have the FSF's version of emacs installed on your system, it can
       interact with the Perl debugger to provide an integrated software
       development environment reminiscent of its interactions with C debug-
       gers.

       Perl comes with a start file for making emacs act like a syntax-
       directed editor that understands (some of) Perl's syntax.  Look in the
       emacs directory of the Perl source distribution.

       A similar setup by Tom Christiansen for interacting with any vendor-
       shipped vi and the X11 window system is also available.	This works
       similarly to the integrated multiwindow support that emacs provides,
       where the debugger drives the editor.  At the time of this writing,
       however, that tool's eventual location in the Perl distribution was
       uncertain.

       Users of vi should also look into vim and gvim, the mousey and windy
       version, for coloring of Perl keywords.

       Note that only perl can truly parse Perl, so all such CASE tools fall
       somewhat short of the mark, especially if you don't program your Perl
       as a C programmer might.

       The Perl Profiler

       If you wish to supply an alternative debugger for Perl to run, just
       invoke your script with a colon and a package argument given to the -d
       flag.  The most popular alternative debuggers for Perl is the Perl pro-
       filer.  Devel::DProf is now included with the standard Perl distribu-
       tion.  To profile your Perl program in the file mycode.pl, just type:

	   $ perl -d:DProf mycode.pl

       When the script terminates the profiler will dump the profile informa-
       tion to a file called tmon.out.	A tool like dprofpp, also supplied
       with the standard Perl distribution, can be used to interpret the
       information in that profile.

Debugging regular expressions
       "use re 'debug'" enables you to see the gory details of how the Perl
       regular expression engine works. In order to understand this typically
       voluminous output, one must not only have some idea about how regular
       expression matching works in general, but also know how Perl's regular
       expressions are internally compiled into an automaton. These matters
       are explored in some detail in "Debugging regular expressions" in
       perldebguts.

Debugging memory usage
       Perl contains internal support for reporting its own memory usage, but
       this is a fairly advanced concept that requires some understanding of
       how memory allocation works.  See "Debugging Perl memory usage" in
       perldebguts for the details.

SEE ALSO
       You did try the -w switch, didn't you?

       perldebtut, perldebguts, re, DB, Devel::DProf, dprofpp, Dumpvalue, and
       perlrun.

       When debugging a script that uses #! and is thus normally found in
       $PATH, the -S option causes perl to search $PATH for it, so you don't
       have to type the path or "which $scriptname".

	 $ perl -Sd foo.pl

BUGS
       You cannot get stack frame information or in any fashion debug func-
       tions that were not compiled by Perl, such as those from C or C++
       extensions.

       If you alter your @_ arguments in a subroutine (such as with "shift" or
       "pop"), the stack backtrace will not show the original values.

       The debugger does not currently work in conjunction with the -W com-
       mand-line switch, because it itself is not free of warnings.

       If you're in a slow syscall (like "wait"ing, "accept"ing, or "read"ing
       from your keyboard or a socket) and haven't set up your own $SIG{INT}
       handler, then you won't be able to CTRL-C your way back to the debug-
       ger, because the debugger's own $SIG{INT} handler doesn't understand
       that it needs to raise an exception to longjmp(3) out of slow syscalls.



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