Something like

!“A line with exactly 0 or 1 characters, or a line with a sequence of 1 or 3 or more characters, repeated at least twice”!<

Syntactically valid Perl

“Doctor” is a title you become entitled to use by virtue of holding a PhD - you have the option to use it, but nothing compels you to do so if you don’t want to.

Note that the reverse isn’t true - representing yourself as holding a doctorate when you don’t can be a fairly serious crime - if you did for the purposes of getting money from some, then it’s probably some kind of fraud