#!/usr/bin/perl -w
use strict;

die "Usage: ", $0 =~ /([^\/]+)$/, " <filename>\n" unless @ARGV;

$^I = '';                       # We're really brave - no backup file! 

while (<>){
    next unless /./;            # Skip empty lines
    tr/A-Z/a-z/;                # Lowercase the lot
    s#^(?!http://)#http://#;    # Prefix 'http://' if one is missing
    print;
}