=item RXf_NO_INPLACE_SUBST
Added in perl 5.18.0, this flag indicates that a regular expression might
=item RXf_NO_INPLACE_SUBST
Added in perl 5.18.0, this flag indicates that a regular expression might
instance it might contain lookbehind, or assign to non-magical variables
(such as $REGMARK and $REGERROR) during matching. C<s///> will skip
certain optimisations when this is set.
instance it might contain lookbehind, or assign to non-magical variables
(such as $REGMARK and $REGERROR) during matching. C<s///> will skip
certain optimisations when this is set.