If you want mcarray to only contain stuff from the new level, you can either remove everything from it:
Code:
while (mcarray.length > 0){
mcarray.pop();
}
Or, if you don't need mcarray to point to the same actual array, you can just set it to a new empty array:
If mcarray contains things you need to keep, then you'll need a way of determining whether to keep or discard an object.
Code:
for (var i:int = mcarray.length-1; i >=0; i--){
if (shouldDiscard(mcarray[i])){
mcarray.splice(i, 1);
}
}
where you need to define the shouldDiscard function.