DB<2> n
main::(pm_135391.pl:3):   my $key = lc $_;
  DB<2> n
main::(pm_135391.pl:4):   next if $seen{$key}++;
  DB<2> n
main::(pm_135391.pl:5):   my $signature = join "", sort split //, $key;
  DB<2> x %seen
0  "abby \cM"
1  1