Returns a true value if EXPR is a reference, false otherwise. If EXPR is not specified, $_ will be used. The value returned depends on the type of thing the reference is a reference to. Builtin types include:
SCALAR ARRAY HASH CODE REF GLOB LVALUEIf the referenced object has been blessed into a package, then that package name is returned instead. You can think of ref as a typeof operator.
if (ref($r) eq "HASH") { print "r is a reference to a hash.\n"; } unless (ref($r)) { print "r is not a reference at all.\n"; } if (UNIVERSAL::isa($r, "HASH")) { # for subclassing print "r is a reference to something that isa hash.\n"; }See also perlref.