ref

• 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
      Regexp

  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($r) eq "HASH") {
  	print "r is a reference to a hash.\n";
      }
      unless (ref($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().

  The result Regexp indicates that the argument is a regular expression resulting from qr//.

  See also perlref.