phpman > perldoc > DEBUG(0)

Found in /usr/share/perl/5.34/pod/perlfaq3.pod
  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).