Returns a non-empty string if EXPR is a reference, the empty string otherwise. If EXPR is not specified, $_
will be used. The value returned depends on the type of thing the reference is a reference to.
Builtin types include:
SCALAR
ARRAY
HASH
CODE
REF
GLOB
LVALUE
FORMAT
IO
VSTRING
Regexp
You can think of ref
as a typeof
operator.
if (ref($r) eq "HASH") {
print "r is a reference to a hash.\n";
}
unless (ref($r)) {
print "r is not a reference at all.\n";
}
The return value LVALUE
indicates a reference to an lvalue that is not a variable. You get this from taking the reference of function calls like pos
or substr
. VSTRING
is returned if the reference points to a version string.
The result Regexp
indicates that the argument is a regular expression resulting from qr//
.
If the referenced object has been blessed into a package, then that package name is returned instead. But don't use that, as it's now considered "bad practice". For one reason, an object could be using a class called Regexp
or IO
, or even HASH
. Also, ref
doesn't take into account subclasses, like isa
does.
Instead, use blessed
(in the Scalar::Util module) for boolean checks, isa
for specific class checks and reftype
(also from Scalar::Util) for type checks. (See perlobj for details and a blessed
/isa
example.)
See also perlref.