<b_jonas> learn ayacc is ais523\'s yacc parser generator implementation, get it from (darcs clone http://nethack4.org/projects/ayacc) or a snapshot from "http://nethack4.org/pastebin/ayacc-2020-04.tar.gz".

#!/usr/bin/perl -w
my $bin = $ENV{"HACKENV"}."/bin"; if (defined($_=shift)) { s/ *$//;  s/ +/ @ /g; exec "$bin/@", $_ . " ? welcome.is"; } else { exec "$bin/?", "welcome.is"; }