http://www.perlmonks.org?node_id=1009576


in reply to can understand one line of code

s### is the substitution operator using the # character as the delimiter instead of the more conventional s/// delimiters. The $ denotes the end of the string (perlre).

Tip #6 from the Basic debugging checklist: B::Deparse can help identify this.

Update: correction thanks to johngg