#!/usr/bin/perl

use strict;
use warnings;
use CGI;

my $q = CGI->new();

sub url_query_string {
  my ($q) = @_;

  # get the names of all URL parameters
  my @params = grep { length($_) } $q->url_param;

  return (@params > 0 ? '?' : '').join('&',map {
    # $q->url_param returns unescaped values so we have to escape them
    # again
    sprintf("%s=%s",$_,CGI::escape($q->url_param($_)))
  } @params);
}

print $q->header('text/plain'),
  $q->url(-absolute => 1).url_query_string($q),"\n";