The second stackoverflow answer you received (from drmrgd — if that is indeed the selfsame monk cavorting without the precincts of Monastery) is a succinct and very Perlish solution. For extra credit on your assignment, expand that approach to capture and display the actual words that contain each letter. The printed output might look something like:

Number of words found for each letter:
A: 3 (AXE CAT TRANCE)
B: 0
C: 2 (CAT TRANCE)
D: 2 (DOG FOOD)
E: 2 (AXE TRANCE)
F: 1 (FOOD)
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