$lterm = 2;                      # lterm = 2
$rterm = 2;                      # rterm = 2

$#add = $lterm; pop(@add);       # add = lterm
push(@acc, @add);                # acc += add

$#add = $rterm; pop(@add);       # add = rterm
push(@acc, @add);                # acc += add

push(@acc, 1); $sum = $#acc;     # sum = acc
print("$sum\n");