Please don't do that, unless you are planning on sticking with the same (tested) perl version forever. perldoc perlvar says:

$^H WARNING: This variable is strictly for internal use only. Its availability, behavior, and contents are subject to change without notice.

and

%^H WARNING: This variable is strictly for internal use only. Its availability, behavior, and contents are subject to change without notice.

See perldoc perlre "Creating custom RE engines" for the documented way to overload regular expressions.