To keep this on topic, if you use the the Perl shell (alt., but not to be confused with the other Perl shells), you should be able to do something like ...

  # UNTESTED!
$Psh::prompt = sub {
    my $progress = get_progress();
    "($progress%) psh\$ ";
}
[download]

... where get_progress() does something similar to your csh code.

    --k.