#ref EXPR

#ref

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.

Perldoc Browser is maintained by Dan Book (DBOOK). Please contact him via the GitHub issue tracker or email regarding any issues with the site itself, search, or rendering of documentation.

The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the Perl issue tracker, the mailing list, or IRC to report any issues with the contents or format of the documentation.