$ perl -MRegexp::Common -e1
$ perl -X -MRegexp::Common -e1
Regexp/Common.pm did not return a true value.
BEGIN failed--compilation aborted.
This is because line 245 is $^W=1. Under -X, that line is turned into $^W=0. That line is the
last statement executed when compiling the file.
Fix is to put a "1;" as the last executable statement in the file right above the POD, the way
we're supposed to.