Make sure the code you are running throught he regex is not interpolated.

perl -e 'print qq|$_\n| for q|tttt $x=123 ttt @c=qw/1 2 3/; tt $xxx tt
+ttt @something|=~/([\$\@\%]\w+)/g'
$x
@c
$xxx
@something
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Update:This code is simplistic. JavaFan's regex (++), above, is much more rigorous.