As follows, if the same characters exists in a list of strings, returns it, if not, returns empty.
I can't think of a good way to solve it. Thanks for help.
(setq str1 '("123abc-de23f" "1abc-f123" "23abc" "23abcd23" "abc31de23"))
(setq str2 '("123abc-de23f" "1abc-f123" "32acd" "23abcd23" "abc31de23"))
(fun str1) ---> ("abc" "23")
(fun str2) ---> nil