my $newposition = $oldposition =~
    s/\+\K([-\d]+)\+([-\d]+)$/ ($1 + $deltax) . '+' . ($2 + $deltay) /er;

##</code><code>##

  $oldposition =~ /^(\d+)x(\d+)\+?([-\d]+)\+?([-\d]+)/;
  my ($newx, $newy) = ($3 + $deltax, $4 + $deltay);
  my $newposition = "${1}x${2}+${newx}+${newy}"