http://www.perlmonks.org?node_id=11137306


in reply to Re^3: Is it safe to use external strings for regexes?
in thread Is it safe to use external strings for regexes?

> is only allowed within the scope of use re 'eval'; with "newer" Perls yes. I noticed that you changed it around 2013, and am thankful for that. *
Um no, "use re 'eval'" has always been required to allow non-literal code blocks in patterns. The big "re eval" rewrite in 5.18.0 just made it smarter, so that for example a literal (and thus safe) code block could be interpolated into a run-time regex without needing the "use re 'eval'": 
use re 'eval'; # ** no longer needed from 5.18.0 onwards
$r = qr/xyz/;
/(?{ foo() })$r/;

[download]

Dave.

In Section Seekers of Perl Wisdom