ref

See the current Perl documentation for ref.

Here is our local, out-dated (pre-5.6) version:

ref - find out the type of thing being referenced

ref EXPR

ref

Returns a TRUE value if EXPR is a reference, FALSE otherwise. If EXPR is not specified, $_ will be used. The value returned depends on the type of thing the reference is a reference to. Builtin types include:

    REF
    SCALAR
    ARRAY
    HASH
    CODE
    GLOB

If the referenced object has been blessed into a package, then that package name is returned instead. You can think of ref() as a typeof() operator.

    if (ref($r) eq "HASH") {
        print "r is a reference to a hash.\n";
    }
    if (!ref($r)) {
        print "r is not a reference at all.\n";
    }

See also the perlref manpage.