Much shorter: print scalar keys %{{map{(lc)x2} /(.)/sg}}; In a oneliner: perl -lne'print if !grep $_ != 15, length, scalar keys %{{map{(lc)x2} /(.)/sg}}' I find two words:

• dermatoglyphics
• uncopyrightable

There'd probably be a few more in a larger list.

Makeshifts last the longest.