#!/usr/bin/perl -w
use strict;
use IO::Dir;

my $oggdir = '/media/tmp/';
ParseDirectory($oggdir);

sub ParseDirectory
{
    my $dir = shift;
    my $d = IO::Dir->new($dir)
       or die "Can not open directory $dir for read!";

    while (defined(my $f = $d->read))
    {
    	if ($f =~ /.*_+.*\.[Oo][Gg]{2}$/) {

            # matching files

            my $new_name = $f;
            $new_name =~ s/_//;    # remove _
            # rename $f to $new_name, etc.
        } else {

            # non-matching files

            # do whatever, set to default, etc.
        }
    }
}