In scalar context, @array (or in your case, @match_A) evaluates to the number of elements in an array. That's not quite what you're looking for; you're looking for the highest index, which is @array - 1^*. But Perl gives you a way to get the index of the last element without doing math; $#array (or in your case, $#match_A) will tell you the index of the ultimate element in the array.

So, for( 4 .. $#match_A ) {....... will do the trick.

^*Note: @array - 1 will also be the index of the highest element, but that assumes you've left $[ alone, which you should. If you've messed with $[ you've committed an egregious foul.