`Try it Both Ways`

        sub cleanup {
          my $i = shift;
          $i =~ s/.*=//s;
          $i =~ tr/01//cd;
          return [ split //, $i ]
        }

How about this?

        sub cleanup {
          local $_ = shift;
          s/.*=//s;
          tr/01//cd;
          return [ split
]
        }