Sifmole,
While the other answers in this thread are good, sometimes it helps to have example code:

#!/usr/bin/perl
use strict;
use warnings;
use WWW::Mechanize;

my $url= 'http://10.11.12.13/password.html';
my $mech = WWW::Mechanize->new( autocheck => 1 );
$mech->credentials(
    '10.11.12.13:80',
    'ABCDEF',
    'admin' => 'password'
);
$mech->get( $url );
print $mech->content();
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