How do I remove duplicate characters and keep the unique one only in Perl?

Question

How do I remove duplicate characters and keep the unique one only. For example, my input is:

EFUAHUU
UUUEUUUUH
UJUJHHACDEFUCU

Expected out

Answer 1

for a file containing the data you list named foo.txt

python -c "print set(open('foo.txt').read())"