if (stack.size() < 2)
return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION) - checks if there are enough elements/inscriptions.
///
valtype& vch1 = stacktop(-2);
valtype& vch2 = stacktop(-1) - gets the top two items.
///
if (vch1.size() + vch2.size() > MAX_SCRIPT_ELEMENT_SIZE)
return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION) - checks size.
///
vch1.insert(vch1.end(), vch2.begin(), vch2.end());
stack.pop_back() - combines the elements and removes the extra element.