Editing Euphoria (programming language) (section)

==Parameter passing==
Arguments to routines are always passed by value; there is no pass-by-reference facility. However, parameters are allowed to be modified ''locally'' (i.e., within the callee) which is implemented very efficiently as sequences have automatic [[copy-on-write]] semantics. In other words, when you pass a sequence to a routine, initially only a reference to it is passed, but at the point the routine modifies this sequence parameter the sequence is copied and the routine updates only a copy of the original.