How to suppress errors from postmaster log?

I've got a Perl routine that makes use of the DBI to do time expression
conversion. As it accepts several different input formats, it resolves to
evaluating the expression in one of several different ways, ordered by a
heuristic to get the "most likely" format first. However, as a side
effect I get messages like these in my postmaster log file:

ERROR:  Bad timestamp external representation '45 minutes'

I'd like to suppress these, because the appearance of so many ERROR
entries confuses anyone skimming the log. (The DBI layer already
suppresses the appearance of the messages in my STDERR file, but they
still show up in the postmaster log.)

Obviously, I could write better heuristics, so that the "right" format
was always tried first. I'm looking for the easy way out ... some way to
tell Postgres not to report "trivial" errors like this.

--
Jeff Boes                                      vox 269.226.9550 ext 24
Database Engineer                                     fax 269.349.9076
Nexcerpt, Inc.                                 http://www.nexcerpt.com
           ...Nexcerpt... Extend your Expertise