http://www.perlmonks.org?node_id=173524
Category: Utility Scripts
Author/Contact Info Mike Irwin - mikeirw@pobox.com
Description:

I needed to view the contents of a nnml mail directory, but didn't have access to Emacs or Gnus, so I whipped up this simple script to allow me to use mail -f instead. I must say that I'm a Perl newbie, so it may need some work. If so, I'll appreciate any comments.

A quick note: I did not include any code to match Gcc'ed emails (which doesn't generate a From header), so you may need to add that before running.

#!/usr/bin/perl -w
#
# Turn a Gnus nnml file into mbox format.  Prints to STDOUT.
# Usage: nnml2mbox files ...

use strict;
use File::Find;

my @nnml_files;
find sub {
    push @nnml_files, $File::Find::name
      if /^\d+/;
}, @ARGV;
@ARGV = @nnml_files;
while (<>) {
    s/^X-From-Line:/\nFrom/;
    print;
}