Well, this site (i.e. PerlMonks) is full of Perl puzzles.
There's new troubleshooting puzzles in Seekers of Perl Wisdom
For really advanced puzzles, try determining how any code posted to
Nearly every Perl book I've ever read has had multiple instances of:
"XXX is left as an exercise to the reader".
While I'm happy to be corrected, I suspect O'Reilly
has the largest collection of Perl books.
I wasn't intending to post any particular title but, when checking the URL for O'Reilly,
I did notice Games, Diversions & Perl Culture
which is possibly the type of thing you're looking for.
A general Internet search may be better but be prepared for a large result set unless you're specific:
googling just 'perl book' indicated over 6 million results.