sub _mapone
 {
 my ($code, $counter)= @_;
 my $list= (($counter&1) == 0) ? \@two_syllable_words : \@three_syllable_words;
 my $result= $$list[$code];
 die unless defined $result;  # internal error -- can't happen.
 return $result;
 }

sub list
 {
 my $x= shift; 
 # delete leading zeros
 $x =~ s/^\0+//;
 my $counter= 0;
 return map { _mapone ($_, $counter++) } (unpack ("C*", $x));
 }