in reply to RFC: A new module to help avoid running multiple instances of the same script (via cron, for example)

You need the Highlander solution ("there can be only one").

-- Randal L. Schwartz, Perl hacker

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.