B::Deparse(3) Perl Programmers Reference Guide B::Deparse(3)NAMEB::Deparse - Perl compiler backend to produce perl code
SYNOPSIS
perl -MO=Deparse[,-uPACKAGE][,-p][,-l][,-sLETTERS] prog.pl
DESCRIPTIONB::Deparse is a backend module for the Perl compiler that
generates perl source code, based on the internal compiled
structure that perl itself creates after parsing a
program. The output of B::Deparse won't be exactly the
same as the original source, since perl doesn't keep track
of comments or whitespace, and there isn't a one-to-one
correspondence between perl's syntactical constructions
and their compiled form, but it will often be close. When
you use the -p option, the output also includes
parentheses even when they are not required by precedence,
which can make it easy to see if perl is parsing your
expressions the way you intended.
Please note that this module is mainly new and untested
code and is still under development, so it may change in
the future.
OPTIONS
As with all compiler backend options, these must follow
directly after the '-MO=Deparse', separated by a comma but
not any white space.
-p Print extra parentheses. Without this option,
B::Deparse includes parentheses in its output only
when they are needed, based on the structure of your
program. With -p, it uses parentheses (almost)
whenever they would be legal. This can be useful if
you are used to LISP, or if you want to see how perl
parses your input. If you say
if ($var & 0x7f == 65) {print "Gimme an A!"}
print ($which ? $a : $b), "\n";
$name = $ENV{USER} or "Bob";
B::Deparse,-p will print
if (($var & 0)) {
print('Gimme an A!')
};
(print(($which ? $a : $b)), '???');
(($name = $ENV{'USER'}) or '???')
which probably isn't what you intended (the '???' is a
sign that perl optimized away a constant value).
-uPACKAGE
Normally, B::Deparse deparses the main code of a
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B::Deparse(3) Perl Programmers Reference Guide B::Deparse(3)
program, all the subs called by the main program (and
all the subs called by them, recursively), and any
other subs in the main:: package. To include subs in
other packages that aren't called directly, such as
AUTOLOAD, DESTROY, other subs called automatically by
perl, and methods, which aren't resolved to subs until
runtime, use the -u option. The argument to -u is the
name of a package, and should follow directly after
the 'u'. Multiple -u options may be given, separated
by commas. Note that unlike some other backends,
B::Deparse doesn't (yet) try to guess automatically
when -u is needed -- you must invoke it yourself.
-l Add '#line' declarations to the output based on the
line and file locations of the original code.
-sLETTERS
Tweak the style of B::Deparse's output. At the moment,
only one style option is implemented:
C Cuddle elsif, else, and continue blocks. For
example, print
if (...) {
...
} else {
...
}
instead of
if (...) {
...
}
else {
...
}
The default is not to cuddle.
BUGS
See the 'to do' list at the beginning of the module file.
AUTHOR
Stephen McCamant <alias@mcs.com>, based on an earlier
version by Malcolm Beattie <mbeattie@sable.ox.ac.uk>.
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