Personally, I prefer Mail::IMAPClient. It obviously isn't necessary to delete the messages like I do below, but that's the snippet of code that I have in my script. Check out the doc to see the other functions available.

use Mail::IMAPClient;

my @folders = qw( INBOX saved-messages folder1 folder2 );

my $imap = Mail::IMAPClient->new( Server => 'mail.server.com:143',
 User => 'user',
 Password => 'pass')
  or die "IMAP failure: $@";

foreach my $folder (@folders) {
  $imap->select($folder)
    or die "Select failure: $!";
  my @msgs = $imap->search('ALL')
    or die "Search error: $!";
  foreach my $msg (@msgs) {
    if ($imap->size($msg) > 100000) { # 100k
      $imap->delete_message($msg);
      next;
    }
  }
  $imap->expunge($folder);
  $imap->close($folder);
}
$imap->logout();
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