What's the difference between tr/// and s/// when using regex in Perl?

Question

I was wondering when one should use s/// over tr/// when working with regular expressions in Perl?

Answer 1

tr/// is not a regular expression operator. It is suitable (and faster than s///) for substitutions of one single character with another single character, or (with the d modifier) substituting a single character with zero characters.

s/// should be used for anything more complicated than the narrow use cases of tr.