How safe is Safe.pm?

Recently, deciding to do some improvements to RegexLab, I decided Safe be best employed, so I did a quick search on perlmonks and came accross

How to use LWP::Simpe inside a safe compartment? (unresolved - probably need to permit some network opcodes)
use Safe and CGI; (a nice little demo)
The proper use of Safe(lesson: lexicals ain't globals)
How Safe is Safe::? (warranty discussion - not related)
Known security issues with Safe.pm? is right on topic, but there is no answer ( and my question is more to the comments of ask ).
Mileage with safe, Perl sandbox, Safe / @ISA Problem

Now I come accross Safe.pm is not safe in which ask says

By returning the right values from the safe compartment it's quite possibly to "break out" of it.

and someone in the cb said the same thing (Safe isn't truly safe), so can somebody explain to me why/how?

Code examples work best.

P.S.

I am aware of Safe::Hole. I did search perlmonks for previous discussion ask mentions that discuss the insecurity of Safe.pm, but turned up nothing.

 

______crazyinsomniac_____________________________ Of all the things I've lost, I miss my mind the most. perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"