from man perlobj: 
       isa(CLASS)
           "isa" returns true if its object is blessed into a subclass of
           "CLASS"

           You can also call "UNIVERSAL::isa" as a subroutine with two argu-
           ments.  The first does not need to be an object or even a refer-
           ence.  This allows you to check what a reference points to, or
           whether something is a reference of a given type. Example

               if(UNIVERSAL::isa($ref, 'ARRAY')) {
                   #...
               }

           To determine if a reference is a blessed object, you can write

               print "It's an object\n" if UNIVERSAL::isa($val, 'UNIVERSAL');

UNIVERSIAL::isa( $thing, "CLASS" ) is a far superior method than ref( $thing ) eq 'CLASS', since the latter does not cater for inheritance.

But I never saw that and I think that this is very wrong, specially in OO style, since you are accessing/changing it's internal structure/attributes directly, and not by methods!

try reading perldoc perlobj!
calling UNIVERSAL::isa does not "access/change internal structure/attributes" -- it is the OO equivalent of a class/static method call in java or c++.

In reply to Re: Re: Is "ref $date eq 'ARRAY'" wrong? What a mess! by Anonymous Monk
in thread Is "ref $date eq 'ARRAY'" wrong? by bronto

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