if ( $act eq '-a' ) {
  %validchars = map { $_ => uc $_ }
                map { pack "C", $_ } ( 0 .. 255 );
} elsif ( $act eq '-c' ) {
  %validchars = map { $_ => $_ }
                map { pack "C", $_ } ( ord('A').. ord('Z'), ord('a')..ord('z') );
};