|Perl: the Markov chain saw|
Answer: Is it possible to do pass by reference in Perl?by Russ (Deacon)
|on Mar 05, 2002 at 19:32 UTC||Need Help??|
One might argue that Perl always does Pass-By-Reference, but protects us from ourselves.
@_ holds the arguments passed to a subroutine, and it is common idiom to see something like:
Why is that? Why don't we just use the @_ array directly?
First, there is the laudable goal of more readable code, which is sufficient reason, in itself, to rename variables away from cryptic things like $_. But really, we copy values out of @_ because (from the man page) "its elements are aliases for the actual scalar parameters."
In short, this means that if you modify an element of @_ in your subroutine, you are also modifying the original argument. This is almost never the expected behavior! Further, if the argument is not updatable (like a literal value, or a constant), your program will die with an error like "Modification of a read-only value attempted."
will print out:
So, yes, you can do pass-by-reference in Perl, even without backslashes; but it is almost always better (some would leave out the "almost" in this statement) to make your caller explicitly pass you a reference if you intend to modify a value.