my $cat = undef;
while (my $line = <FILE>) {
    @items = split('|', $line);
    if ($cat ne $items[2]) {
        close OUTFILE if (defined $cat);
        open OUTFILE, ">>some_filename";
        $cat = $items[2];
    } 
    print OUTFILE ## Whatever ###;
}
close OUTFILE;