http://qs321.pair.com?node_id=204134
Description: I find really interesting the capability of mozilla to open new URLs in new tabs of a already running mozilla process. Still i find the syntax of the command awkward and not really usable. So I added the following snippet to my PATH. It's really simple, but makes the trick.

NB: tested with Mozilla 1.1. It should work even with Mozilla 1.0 but i'm pretty sure it won't work for previous versions.

#!/usr/bin/perl

use strict;

use constant USAGE => <<EOU;
USAGE:
$0 (filename|URL|mailto:email\@addre.ss)
EOU

$_ = shift;
my $command = 'openURL(%s, new-tab)';

SWITCH: {
    s!^(www\..+)!http://$1!;
    m!^(ftp|http|file)://! and last;
    s!^mailto:!! and do {
        $command = 'mailto(%s)';
        last;
    };
    -r and do {
        require Cwd;
        $_ = 'file://' . Cwd::abs_path( $_ );
        last;
    };
    print USAGE and exit;
}

system "mozilla", "-remote", sprintf($command, $_);