FAQ 3.5 How do I debug my Perl programs?
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3.5: How do I debug my Perl programs?
(contributed by brian d foy)
Before you do anything else, you can help yourself by ensuring that you
let Perl tell you about problem areas in your code. By turning on
warnings and strictures, you can head off many problems before they get
too big. You can find out more about these in strict and warnings.
#!/usr/bin/perl
use strict;
use warnings;
Beyond that, the simplest debugger is the "print" function. Use it to
look at values as you run your program:
print STDERR "The value is [$value]\n";
The "Data::Dumper" module can pretty-print Perl data structures:
use Data::Dumper qw( Dumper );
print STDERR "The hash is " . Dumper( \%hash ) . "\n";
Perl comes with an interactive debugger, which you can start with the
"-d" switch. It's fully explained in perldebug.
If you'd like a graphical user interface and you have Tk, you can use
"ptkdb". It's on CPAN and available for free.
If you need something much more sophisticated and controllable, Leon
Brocard's Devel::ebug (which you can call with the -D switch as -Debug)
gives you the programmatic hooks into everything you need to write your
own (without too much pain and suffering).
You can also use a commercial debugger such as Affrus (Mac OS X), Komodo
from Activestate (Windows and Mac OS X), or EPIC (most platforms).
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