Your code is based on 4 normal goto plus one which is called inside Card() to leave the sub, which is called 4 more times, plus 2 times inside Cover() which is called thrice.

These are 16 jumps in total.

All this is "determined" on randomized data.

Respect, you put the spaghetti into spaghetti code.

That's highly unpredictable, and the missing code indentation doesn't make it easier to grasp.

If your problems didn't or rarely happened before but are now, one reason might be differences in arithmetics.

We just had a talk at the London Perl Workshop about an undiscovered bug only showing up if the same code and Perl version was run on a newer Ubuntu version.

The precision jumped and the code crashed because a threshold was exceeded.

Nota Bene: the code was already buggy before, but this went unnoticed.