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

Here is a solution, that I think should work faster than the lookahead one, but is not regexp-based and uses hashtable.

perl -n -e '%seen=();' -e 'for (split //) {print unless $seen{$_}++;}' 

It splits every line into characters and prints only the first appearance by counting appearances inside %seen hashtable