Returns a non-empty string if EXPR is a reference, the empty
string 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:
If the referenced object has been blessed into a package, then that package
name is returned instead. You can think of
ref as a
indicates that the argument is a regular expression
See also perlref.