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

while (<>) {
  if (/foo/) {
    # ... change line :
    $_ = "This line was changed ($_)";
  };
};

##</code><code>##

perl -pe '/foo/ and $_ = "This line was changed ($_)"'

##</code><code>##

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web