potential security risk. Note that this pragma is ignored when the regular
expression is obtained from tainted data, i.e. evaluation is always
disallowed with tainted regular expressions. See L<perlre/(?{ code })>
-and L<perlre/(?{ code })>.
+and L<perlre/(??{ code })>.
For the purpose of this pragma, interpolation of precompiled regular
expressions (i.e., the result of C<qr//>) is I<not> considered variable