my @from = sort { substr( $a, 46, -4) <=> substr( $b, 46, -4) } <$fromdir/*.las>;
my $oldbase = '';
my $next = 0;
for my $from (@from) {
	my $base = substr( $from, 35, 11 );
	if ( $base ne $oldbase ) {
		$oldbase = $base;
		my $last = ( sort{ substr( $a, 22, -4) <=> substr( $b, 22, -4) } <$todir/$base*.las> ) [-1];
		$next = substr( $next, 22, -4) + 1;
	}
	rename $from, "$todir/$basex$next.las";
	$next++;
}