#!/usr/bin/perl
use strict;
use warnings;

open my $file, "<", "petpages" or die "Could not open petpages: $!";
open my $new, ">", "petpages.new" or die "Could not open petpages.new: $!";

while (my $line = <$file>) {
   $line =~ tr/A-Z/a-z/;
   print $new "http://$line";
}

close $file;
close $new;
rename "petpages.new", "petpages";