if ($output = `firefox`)
    {print "no browser found\n"}

##</code><code>##

BROWSER: {
    for my $dir (split /:/, $ENV{PATH}) {
        for my $browser (qw(firefox mozilla opera konqueror)) {
            if (-x "$dir/$browser") {
                system "$dir/$browser"   # or "$dir/$browser &" to background
                    and die "running $browser returned $?\n";
                last BROWSER;
            }
        }
    }
    print "no browser found.\n";
}