my $flag = 0;
$cnv_reference_ref->bind("location$x", '<B1-ButtonPress>' => [sub { $flag = 1 }, "$i", "1"]);
$cnv_reference_ref->bind("location$x", '<B1-ButtonRelease>' => [sub { $flag = 0 }, "$i", "1"]);
$cnv_reference_ref->bind("location$x", '<B1-Motion>' => [sub { return unless $flag; click_select(@_) }, "$i", "1"]);