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
perlcompile
 
PERLCOMPILE(1)	       Perl Programmers Reference Guide 	PERLCOMPILE(1)



NAME
       perlcompile - Introduction to the Perl Compiler-Translator

DESCRIPTION
       Perl has always had a compiler: your source is compiled into an inter-
       nal form (a parse tree) which is then optimized before being run.
       Since version 5.005, Perl has shipped with a module capable of inspect-
       ing the optimized parse tree ("B"), and this has been used to write
       many useful utilities, including a module that lets you turn your Perl
       into C source code that can be compiled into a native executable.

       The "B" module provides access to the parse tree, and other modules
       ("back ends") do things with the tree.  Some write it out as bytecode,
       C source code, or a semi-human-readable text.  Another traverses the
       parse tree to build a cross-reference of which subroutines, formats,
       and variables are used where.  Another checks your code for dubious
       constructs.  Yet another back end dumps the parse tree back out as Perl
       source, acting as a source code beautifier or deobfuscator.

       Because its original purpose was to be a way to produce C code corre-
       sponding to a Perl program, and in turn a native executable, the "B"
       module and its associated back ends are known as "the compiler", even
       though they don't really compile anything.  Different parts of the com-
       piler are more accurately a "translator", or an "inspector", but people
       want Perl to have a "compiler option" not an "inspector gadget".  What
       can you do?

       This document covers the use of the Perl compiler: which modules it
       comprises, how to use the most important of the back end modules, what
       problems there are, and how to work around them.

       Layout

       The compiler back ends are in the "B::" hierarchy, and the front-end
       (the module that you, the user of the compiler, will sometimes interact
       with) is the O module.  Some back ends (e.g., "B::C") have programs
       (e.g., perlcc) to hide the modules' complexity.

       Here are the important back ends to know about, with their status
       expressed as a number from 0 (outline for later implementation) to 10
       (if there's a bug in it, we're very surprised):

       B::Bytecode
	   Stores the parse tree in a machine-independent format, suitable for
	   later reloading through the ByteLoader module.  Status: 5 (some
	   things work, some things don't, some things are untested).

       B::C
	   Creates a C source file containing code to rebuild the parse tree
	   and resume the interpreter.	Status: 6 (many things work ade-
	   quately, including programs using Tk).

       B::CC
	   Creates a C source file corresponding to the run time code path in
	   the parse tree.  This is the closest to a Perl-to-C translator
	   there is, but the code it generates is almost incomprehensible
	   because it translates the parse tree into a giant switch structure
	   that manipulates Perl structures.  Eventual goal is to reduce
	   (given sufficient type information in the Perl program) some of the
	   Perl data structure manipulations into manipulations of C-level
	   ints, floats, etc.  Status: 5 (some things work, including uncom-
	   plicated Tk examples).

       B::Lint
	   Complains if it finds dubious constructs in your source code.  Sta-
	   tus: 6 (it works adequately, but only has a very limited number of
	   areas that it checks).

       B::Deparse
	   Recreates the Perl source, making an attempt to format it coher-
	   ently.  Status: 8 (it works nicely, but a few obscure things are
	   missing).

       B::Xref
	   Reports on the declaration and use of subroutines and variables.
	   Status: 8 (it works nicely, but still has a few lingering bugs).

Using The Back Ends
       The following sections describe how to use the various compiler back
       ends.  They're presented roughly in order of maturity, so that the most
       stable and proven back ends are described first, and the most experi-
       mental and incomplete back ends are described last.

       The O module automatically enabled the -c flag to Perl, which prevents
       Perl from executing your code once it has been compiled.  This is why
       all the back ends print:

	 myperlprogram syntax OK

       before producing any other output.

       The Cross Referencing Back End

       The cross referencing back end (B::Xref) produces a report on your pro-
       gram, breaking down declarations and uses of subroutines and variables
       (and formats) by file and subroutine.  For instance, here's part of the
       report from the pod2man program that comes with Perl:

	 Subroutine clear_noremap
	   Package (lexical)
	     $ready_to_print   i1069, 1079
	   Package main
	     $& 	       1086
	     $. 	       1086
	     $0 	       1086
	     $1 	       1087
	     $2 	       1085, 1085
	     $3 	       1085, 1085
	     $ARGV	       1086
	     %HTML_Escapes     1085, 1085

       This shows the variables used in the subroutine "clear_noremap".  The
       variable $ready_to_print is a my() (lexical) variable, introduced
       (first declared with my()) on line 1069, and used on line 1079.	The
       variable $& from the main package is used on 1086, and so on.

       A line number may be prefixed by a single letter:

       i   Lexical variable introduced (declared with my()) for the first
	   time.

       &   Subroutine or method call.

       s   Subroutine defined.

       r   Format defined.

       The most useful option the cross referencer has is to save the report
       to a separate file.  For instance, to save the report on myperlprogram
       to the file report:

	 $ perl -MO=Xref,-oreport myperlprogram

       The Decompiling Back End

       The Deparse back end turns your Perl source back into Perl source.  It
       can reformat along the way, making it useful as a de-obfuscator.  The
       most basic way to use it is:

	 $ perl -MO=Deparse myperlprogram

       You'll notice immediately that Perl has no idea of how to paragraph
       your code.  You'll have to separate chunks of code from each other with
       newlines by hand.  However, watch what it will do with one-liners:

	 $ perl -MO=Deparse -e '$op=shift||die "usage: $0
	 code [...]";chomp(@ARGV=<>)unless@ARGV; for(@ARGV){$was=$_;eval$op;
	 die$@ if$@; rename$was,$_ unless$was eq $_}'
	 -e syntax OK
	 $op = shift @ARGV || die("usage: $0 code [...]");
	 chomp(@ARGV = ) unless @ARGV;
	 foreach $_ (@ARGV) {
	     $was = $_;
	     eval $op;
	     die $@ if $@;
	     rename $was, $_ unless $was eq $_;
	 }

       The decompiler has several options for the code it generates.  For
       instance, you can set the size of each indent from 4 (as above) to 2
       with:

	 $ perl -MO=Deparse,-si2 myperlprogram

       The -p option adds parentheses where normally they are omitted:

	 $ perl -MO=Deparse -e 'print "Hello, world\n"'
	 -e syntax OK
	 print "Hello, world\n";
	 $ perl -MO=Deparse,-p -e 'print "Hello, world\n"'
	 -e syntax OK
	 print("Hello, world\n");

       See B::Deparse for more information on the formatting options.

       The Lint Back End

       The lint back end (B::Lint) inspects programs for poor style.  One pro-
       grammer's bad style is another programmer's useful tool, so options let
       you select what is complained about.

       To run the style checker across your source code:

	 $ perl -MO=Lint myperlprogram

       To disable context checks and undefined subroutines:

	 $ perl -MO=Lint,-context,-undefined-subs myperlprogram

       See B::Lint for information on the options.

       The Simple C Back End

       This module saves the internal compiled state of your Perl program to a
       C source file, which can be turned into a native executable for that
       particular platform using a C compiler.	The resulting program links
       against the Perl interpreter library, so it will not save you disk
       space (unless you build Perl with a shared library) or program size.
       It may, however, save you startup time.

       The "perlcc" tool generates such executables by default.

	 perlcc myperlprogram.pl

       The Bytecode Back End

       This back end is only useful if you also have a way to load and execute
       the bytecode that it produces.  The ByteLoader module provides this
       functionality.

       To turn a Perl program into executable byte code, you can use "perlcc"
       with the "-B" switch:

	 perlcc -B myperlprogram.pl

       The byte code is machine independent, so once you have a compiled mod-
       ule or program, it is as portable as Perl source (assuming that the
       user of the module or program has a modern-enough Perl interpreter to
       decode the byte code).

       See B::Bytecode for information on options to control the optimization
       and nature of the code generated by the Bytecode module.

       The Optimized C Back End

       The optimized C back end will turn your Perl program's run time code-
       path into an equivalent (but optimized) C program that manipulates the
       Perl data structures directly.  The program will still link against the
       Perl interpreter library, to allow for eval(), "s///e", "require", etc.

       The "perlcc" tool generates such executables when using the -O switch.
       To compile a Perl program (ending in ".pl" or ".p"):

	 perlcc -O myperlprogram.pl

       To produce a shared library from a Perl module (ending in ".pm"):

	 perlcc -O Myperlmodule.pm

       For more information, see perlcc and B::CC.

Module List for the Compiler Suite
       B   This module is the introspective ("reflective" in Java terms) mod-
	   ule, which allows a Perl program to inspect its innards.  The back
	   end modules all use this module to gain access to the compiled
	   parse tree.	You, the user of a back end module, will not need to
	   interact with B.

       O   This module is the front-end to the compiler's back ends.  Normally
	   called something like this:

	     $ perl -MO=Deparse myperlprogram

	   This is like saying "use O 'Deparse'" in your Perl program.

       B::Asmdata
	   This module is used by the B::Assembler module, which is in turn
	   used by the B::Bytecode module, which stores a parse-tree as byte-
	   code for later loading.  It's not a back end itself, but rather a
	   component of a back end.

       B::Assembler
	   This module turns a parse-tree into data suitable for storing and
	   later decoding back into a parse-tree.  It's not a back end itself,
	   but rather a component of a back end.  It's used by the assemble
	   program that produces bytecode.

       B::Bblock
	   This module is used by the B::CC back end.  It walks "basic
	   blocks".  A basic block is a series of operations which is known to
	   execute from start to finish, with no possibility of branching or
	   halting.

       B::Bytecode
	   This module is a back end that generates bytecode from a program's
	   parse tree.	This bytecode is written to a file, from where it can
	   later be reconstructed back into a parse tree.  The goal is to do
	   the expensive program compilation once, save the interpreter's
	   state into a file, and then restore the state from the file when
	   the program is to be executed.  See "The Bytecode Back End" for
	   details about usage.

       B::C
	   This module writes out C code corresponding to the parse tree and
	   other interpreter internal structures.  You compile the correspond-
	   ing C file, and get an executable file that will restore the inter-
	   nal structures and the Perl interpreter will begin running the pro-
	   gram.  See "The Simple C Back End" for details about usage.

       B::CC
	   This module writes out C code corresponding to your program's oper-
	   ations.  Unlike the B::C module, which merely stores the inter-
	   preter and its state in a C program, the B::CC module makes a C
	   program that does not involve the interpreter.  As a consequence,
	   programs translated into C by B::CC can execute faster than normal
	   interpreted programs.  See "The Optimized C Back End" for details
	   about usage.

       B::Concise
	   This module prints a concise (but complete) version of the Perl
	   parse tree.	Its output is more customizable than the one of
	   B::Terse or B::Debug (and it can emulate them). This module useful
	   for people who are writing their own back end, or who are learning
	   about the Perl internals.  It's not useful to the average program-
	   mer.

       B::Debug
	   This module dumps the Perl parse tree in verbose detail to STDOUT.
	   It's useful for people who are writing their own back end, or who
	   are learning about the Perl internals.  It's not useful to the
	   average programmer.

       B::Deparse
	   This module produces Perl source code from the compiled parse tree.
	   It is useful in debugging and deconstructing other people's code,
	   also as a pretty-printer for your own source.  See "The Decompiling
	   Back End" for details about usage.

       B::Disassembler
	   This module turns bytecode back into a parse tree.  It's not a back
	   end itself, but rather a component of a back end.  It's used by the
	   disassemble program that comes with the bytecode.

       B::Lint
	   This module inspects the compiled form of your source code for
	   things which, while some people frown on them, aren't necessarily
	   bad enough to justify a warning.  For instance, use of an array in
	   scalar context without explicitly saying "scalar(@array)" is some-
	   thing that Lint can identify.  See "The Lint Back End" for details
	   about usage.

       B::Showlex
	   This module prints out the my() variables used in a function or a
	   file.  To get a list of the my() variables used in the subroutine
	   mysub() defined in the file myperlprogram:

	     $ perl -MO=Showlex,mysub myperlprogram

	   To get a list of the my() variables used in the file myperlprogram:

	     $ perl -MO=Showlex myperlprogram

	   [BROKEN]

       B::Stackobj
	   This module is used by the B::CC module.  It's not a back end
	   itself, but rather a component of a back end.

       B::Stash
	   This module is used by the perlcc program, which compiles a module
	   into an executable.	B::Stash prints the symbol tables in use by a
	   program, and is used to prevent B::CC from producing C code for the
	   B::* and O modules.	It's not a back end itself, but rather a com-
	   ponent of a back end.

       B::Terse
	   This module prints the contents of the parse tree, but without as
	   much information as B::Debug.  For comparison, "print "Hello,
	   world.""  produced 96 lines of output from B::Debug, but only 6
	   from B::Terse.

	   This module is useful for people who are writing their own back
	   end, or who are learning about the Perl internals.  It's not useful
	   to the average programmer.

       B::Xref
	   This module prints a report on where the variables, subroutines,
	   and formats are defined and used within a program and the modules
	   it loads.  See "The Cross Referencing Back End" for details about
	   usage.

KNOWN PROBLEMS
       The simple C backend currently only saves typeglobs with alphanumeric
       names.

       The optimized C backend outputs code for more modules than it should
       (e.g., DirHandle).  It also has little hope of properly handling "goto
       LABEL" outside the running subroutine ("goto &sub" is okay).  "goto
       LABEL" currently does not work at all in this backend.  It also creates
       a huge initialization function that gives C compilers headaches.
       Splitting the initialization function gives better results.  Other
       problems include: unsigned math does not work correctly; some opcodes
       are handled incorrectly by default opcode handling mechanism.

       BEGIN{} blocks are executed while compiling your code.  Any external
       state that is initialized in BEGIN{}, such as opening files, initiating
       database connections etc., do not behave properly.  To work around
       this, Perl has an INIT{} block that corresponds to code being executed
       before your program begins running but after your program has finished
       being compiled.	Execution order: BEGIN{}, (possible save of state
       through compiler back-end), INIT{}, program runs, END{}.

AUTHOR
       This document was originally written by Nathan Torkington, and is now
       maintained by the perl5-porters mailing list perl5-porters@perl.org.



perl v5.8.8			  2006-01-07			PERLCOMPILE(1)
=208788
+242
(72)