+ } else {
+ if ($promo ne '') {
+ if ($piece eq 'p') {
+ $piece = $promo;
+ } else {
+ $piece = uc($promo);
+ }
+ }
+ }
+ }
+
+ # update the board
+ substr($nb[$from_row], $from_col, 1, '-');
+ substr($nb[$to_row], $to_col, 1, $piece);
+
+ return \@nb;
+}
+
+sub prettyprint_pv {
+ my ($board, @pvs) = @_;
+
+ if (scalar @pvs == 0 || !defined($pvs[0])) {
+ return ();
+ }
+
+ my $pv = shift @pvs;
+ my $from_col = col_letter_to_num(substr($pv, 0, 1));
+ my $from_row = row_letter_to_num(substr($pv, 1, 1));
+ my $to_col = col_letter_to_num(substr($pv, 2, 1));
+ my $to_row = row_letter_to_num(substr($pv, 3, 1));
+ my $promo = substr($pv, 4, 1);
+
+ my $nb = make_move($board, $from_row, $from_col, $to_row, $to_col, $promo);
+ my $piece = substr($board->[$from_row], $from_col, 1);
+
+ if ($piece eq '-') {
+ die "Invalid move $pv";
+ }
+
+ # white short castling
+ if ($pv eq 'e1g1' && $piece eq 'K') {
+ return ('0-0', prettyprint_pv($nb, @pvs));
+ }
+
+ # white long castling
+ if ($pv eq 'e1c1' && $piece eq 'K') {
+ return ('0-0-0', prettyprint_pv($nb, @pvs));
+ }
+
+ # black short castling
+ if ($pv eq 'e8g8' && $piece eq 'k') {
+ return ('0-0', prettyprint_pv($nb, @pvs));
+ }
+
+ # black long castling
+ if ($pv eq 'e8c8' && $piece eq 'k') {
+ return ('0-0-0', prettyprint_pv($nb, @pvs));
+ }
+
+ my $pretty;
+
+ # check if the from-piece is a pawn
+ if (lc($piece) eq 'p') {
+ # attack?
+ if ($from_col != $to_col) {
+ $pretty = substr($pv, 0, 1) . 'x' . substr($pv, 2, 2);