Here is the new version, using URI.
However, I had difficulties to see, how the module allows me to seperate ';' seperated parts of the URI (according to o'reillys "HTTP The definitive Guide" called "parameters', opposed to the well known query-string seperated via '?'), so I strip this of with a regex before I construct the URI-Object.

Feel free to comment on this further, I'd appriciate your feedback.

#!/usr/bin/perl -wT
# creator   : Tom Regner <tomte@tomsdiner.org>
# created   : Mon 13 Jan 2003 01:29:04 PM CET
# version   : $Id: apache_rw.pl,v 1.11 2003/07/02 14:09:57 tom Exp $# 
+copyright : (c) 2002

use strict;
use URI;

#
# change this directive to point to the dir containing the config-file
#
use lib '/path/to/config/file';
use apache_rw_cfg qw($conf);

# loggen?
my $DEBUG = 1;

$| = 1; # unbuffered IO


while (<>) {
    open(LOG, ">>", "apache_rw.log") if $DEBUG; # change !
    my $line = $_;
    my ($uri, $params, $remainder);
    $line =~ s/(;.+)//; # strip of ';'-seperated part (session-id and 
+the like)
    $remainder = $1;

    my $luri = URI->new($line);

    $uri = $luri->path();
    $params = $luri->query();
    $remainder ||= '';

    print LOG $uri . " || " .  $remainder . " || " . $params . "\n" if
+ $DEBUG;

    my ($new_uri, $new_params);

    if ($conf->{$uri}->{'url'}) {
        $new_uri = $conf->{$uri}->{'url'};
        my $didIt = 1;
        my @parm_list = split(/&/, $params);
        $didIt = 0 if @parm_list == 0;
        my @new_parm_list = ();
        if ($didIt) {
            foreach (@parm_list) {
                my ($name,$value) = split('=', $_);
                if (defined($conf->{$uri}->{params}->{$name})) {
                    if ($value =~ m{$conf->{$uri}->{params}->{$name}->
+{regexp}}) {
                        push(@new_parm_list, $conf->{$uri}->{params}->
+{$name}->{name} . '=' . $value);
                    } else {
                        $didIt = 0;
                        print LOG "Param-Value violation" if $DEBUG;
                    }
                } else {
                    $didIt = 0;
                    print LOG "Param-Name violation" if $DEBUG;
                }
            }  
        }
        if ($didIt == 1) {
            $line =  $new_uri . '?';
            $remainder ||= '';
            $line .= join('&', @new_parm_list) . $remainder . "\n";
        } else {
            $line = '/' . "\n";
        }
    } else {
        $line = '/' . "\n";
    }
    close(LOG) if $DEBUG;
    $line = URI->new($line)->canonical;
    print $line;
}
#
[download]

regards,
tomte

Hlade's Law:

If you have a difficult task, give it to a lazy person --
they will find an easier way to do it.