Here's how to cleanly uninstall any Perl module:

#!/usr/local/bin/perl

use ExtUtils::Packlist;
use ExtUtils::Installed;

$ARGV[0] or die "Usage: $0 Module::Name\n";

my $mod = $ARGV[0];

my $inst = ExtUtils::Installed->new();

foreach my $item (sort($inst->files($mod))) {
         print "removing $item\n";
         unlink $item;
}

my $packfile = $inst->packlist($mod)->packlist_file();
print "removing $packfile\n";
unlink $packfile;

The following will sort an array of IP addresses in @in and the sorted IP addresses will be in @out.

@out = sort {
    pack('C4' => $a =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/)
    cmp
    pack('C4' => $b =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/)
} @in;

What this does is it forms a string of four bytes out the IP address octet using the pack() function then sorts it lexicographically.

See also Sorting Section Numbers

The code below is a template for a daemon written in Perl. Use the code below as a starting point when you have to write a program that has to persist in the background to do its things and without a gui.

use POSIX qw(setsid);

chdir '/' or die "Can't chdir to /: $!";
umask 0;
open STDIN, '/dev/null'
    or die "Can't read /dev/null: $!";

#open STDOUT, '>/dev/null'
#    or die "Can't write to /dev/null: $!";

open STDERR, '>/dev/null'
    or die "Can't write to /dev/null: $!";

defined(my $pid = fork)
    or die "Can't fork: $!";

exit if $pid;

setsid or die "Can't start a new session: $!";

while(1) {
    sleep(5);
    print "Hello...n";
}

Note that one of the lines above is commented out to let the output print to the screen. Uncomment this in the final code to silence your program. For more on this code, see this tutorial: http://www.webreference.com/perl/tutorial/9/.

To parse command line arguments passed to a script without using a module, parse @ARGV with the following:

foreach my $arg (@ARGV) {
    $a = 1, next if $arg eq '-a';
    $b = 1, next if $arg eq '-b';
    $c = 1, next if $arg eq '-c';
}

Note: This is good only for boolean (on/off) command line switches.

ptkdb is a graphical Perl debugger. To use it when debugging command line scripts is very straight forward. Just type in the command line:

perl -d:ptkdb script.pl

and you’re good to go.

However, using it to debug CGIs needs some tweaking to your CGI source. Replace the usual

#!/usr/bin/perl

line at the top of the CGI script with this one:

#!/usr/bin/perl -d:ptkdb
BEGIN {$ENV{DISPLAY} = "$ENV{REMOTE_ADDR}:0.0";}

Go to your browser and invoke your CGI and a debugger window should pop up.

Here’s a CGI to display a module’s POD. The module has to be in the $INC. This is great for providing documentation to internal modules.

# save this as showdoc.cgi
#!/usr/local/bin/perl
use strict;

use Pod::Html;
use CGI;
use CGI::Carp qw(fatalsToBrowser);

# Send out the header
print "Content-type: text/html", "\n\n";

my $q = new CGI;

my $module = $q->param('module');
require $module;

$| = 1;

chdir ("/tmp");

my $fullpath = $INC{$module}
    or die "$module not found";

pod2html("--infile=$fullpath", "--flush");

# Clean up the junk left by pod2html
END {
        unlink("pod2html-dircache");
        unlink("pod2html-itemcache");
}

To use this, say you want to view POD for Data::Dumper:

http://localhost/cgi-bin/showdoc.cgi?module=Data/Dumper.pm

Use this to create a skeleton module:

h2xs -AXn Your::Module

To detect a CPU’s endian architecture, use either one of the variables set like so:

$is_big_endian = unpack("h*", pack("s", 1)) =~ /01/;
$is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;

Found in Perlmonks