perlre explains why this is not permitted, and how to make it permitted if you really want to do it...

$string =~ /$re/;

Before Perl knew how to execute interpolated
code within a pattern, this operation was com­
pletely safe from a security point of view,
although it could raise an exception from an
illegal pattern.  If you turn on the "use re
'eval'", though, it is no longer secure, so you
should only do so if you are also using taint
checking.  Better yet, use the carefully con­
strained evaluation within a Safe module.  See
perlsec for details about both these mechanisms.
We're not surrounded, we're in a target-rich environment!

In reply to Re: Regular Expression Question by jasonk
in thread Regular Expression Question by Anonymous Monk

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