Are you sure you meant my @setargs = [ $set1, $set2 ];? If so, and you want to push additional sets onto the array that has $set1 and $set2, do push @{$setargs[0]}, whatever else;. Note that push takes a LIST of things to push; no need to loop and push them one by one.

If you really meant my @setargs = ( $set1, $set2 );, where the array containing the sets is @setargs itself, not in it's first element, just do push @setargs, whatever else;.