Did your use line look like this?

use Regexp::Common

Note the double colon -- not the slash you used in your note.

...and did your error end with a line like this?

BEGIN failed--compilation aborted at 40.pl line 3.

I mention the first because the first thing that occurs to me is that you tried to

use Regexp/Common;

If you used the correct form (as in the first sample above), then IMO, the problem is likely that Regexp::Common is not installed.