regex word that contains same two characters code example

Example 1: count how many characters in the same position are eqial in both strings

sum(1 if c1 == c2 else 0 for c1, c2 in zip(string1, string2))

Example 2: regex match two characters

echo %H#E%L#L%O! | sed 's/[#%]//g'	#replaces every appearance of any of
two characters # and %