>>235 Perl5

for $s (BCDEFGHIJKLMNOPQRSTUVWXYZ, YIZFOADLMWCRUTGSVQKJEHNBP) {
 @a = grep{0>index$s,$_} A..Z;
 print "$s -> @a\n";
}

$ perl 14_235.pl
BCDEFGHIJKLMNOPQRSTUVWXYZ -> A
YIZFOADLMWCRUTGSVQKJEHNBP -> X