[sf-perl] regex problem: append path only if not in list already

[Joseph Brenner]

Yary:

I really like your solution to Lambert's problem.  That idiom of
using \K with a negative lookahead is a new one on me.

I checked it against a few cases though, and I think it fails if
the path is already there in the *first* position.  I tweaked it
a bit and got an alternate version that deals with that:

https://github.com/doomvox/raku-study/blob/main/bin/2021feb28/pcre_regex_to_append_path_non_redundantly.t