I've modified my script with the intention of it working with multiple
messages so that it isn't necessary to execute the piping command as
many times as there are messages.

Mutt:
  The idea is that a user can tag multiple messages and invoke
  "|" to send all the messages to this script at once.  Note
  the documentation for pipe_split and pipe_sep variables in the Mutt
  manual.

  N.B. I haven't really tested this capability with Mutt yet.  I'm
  also in the process of trying to find out why Mutt adds pipe_sep
  after each message even when pipe_split is set (it seems unnecessary
  to me).  I'm waiting for an answer on mutt-dev, but if anyone here
  knows the reason for the current Mutt design, I'd really appreciate
  being filled in.

Mew:
  Mew doesn't yet have support for executing arbitrary shell commands
  on messages marked with `@'.  I've written up some code to do this
  and I'm hoping to have it or something comparable accepted as
  part of Mew.  My current thoughts are to try to emulate the Mutt
  interface as much as possible so that scripts written to work with
  Mutt's piping interface will also work with Mew.

New Version:
  http://mashin.nanoyo.net:81/pkgsrc/mail2cvs.pl

Original Version:
  http://mashin.nanoyo.net:81/pkgsrc/mail2cvs.pl-0.5