I would have to say that your best bet (assuming I understand you correctly) is
Mail::Box or
Mail::Box::Manager. It's located
here.
Assuming that you are using mbox format for your mailboxes:
use Mail::Box::Manager;
my $mgr = Mail::Box::Manager->new;
my $folder = $mgr->open(folder => $ARGV[0])
or die("Mailbox open error: $!");
print $folder->name. ": ".$folder->messages ." Total Messages\n";
# Iterate over the messages
foreach (@$folder) { print "Message $_"; }
$mgr->close()
or die("Mailbox close error: $!");
Untested.