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

From perlop: Quote and Quote-like Operators

Note that tr does not do regular expression character classes such as \d or [:lower:]. The tr operator is not equivalent to the tr(1) utility. If you want to map strings between lower/upper cases, see lc and uc, and in general consider using the s operator if you need regular expressions.