1N/A# that it exists to define. The use of Exporter below is a historical 1N/A# accident that can't be fixed without breaking code. Note that we 1N/A# Exporter. It's bad enough that all classes have a import() method 1N/AUNIVERSAL - base class for ALL classes (blessed references) 1N/A $is_io = $fd->isa("IO::Handle"); 1N/A $is_io = Class->isa("IO::Handle"); 1N/A $sub = $obj->can("print"); 1N/A $sub = Class->can("print"); 1N/A use UNIVERSAL qw( isa can VERSION ); 1N/A $yes = isa $ref, "HASH" ; 1N/A $sub = can $ref, "fandango" ; 1N/A $ver = VERSION $obj ; 1N/AC<UNIVERSAL> is the base class which all bless references will inherit from, 1N/AC<UNIVERSAL> provides the following methods and functions: 1N/A=item C<< $obj->isa( TYPE ) >> 1N/A=item C<< CLASS->isa( TYPE ) >> 1N/A=item C<isa( VAL, TYPE )> 1N/Ais a blessed reference or a string containing a package name 1N/Ais any of the above or an unblessed reference 1N/AWhen used as an instance or class method (C<< $obj->isa( TYPE ) >>), 1N/AC<isa> returns I<true> if $obj is blessed into package C<TYPE> or 1N/Ainherits from package C<TYPE>. 1N/AWhen used as a class method (C<< CLASS->isa( TYPE ) >>: sometimes 1N/Areferred to as a static method), C<isa> returns I<true> if C<CLASS> 1N/Ainherits from (or is itself) the name of the package C<TYPE> or 1N/Ainherits from package C<TYPE>. 1N/AWhen used as a function, like 1N/A use UNIVERSAL qw( isa ) ; 1N/A $yes = isa $h, "HASH"; 1N/A $yes = isa "Foo", "Bar"; 1N/A $yes = UNIVERSAL::isa $a, "ARRAY"; 1N/AC<isa> returns I<true> in the same cases as above and also if C<VAL> is an 1N/Aunblessed reference to a perl variable of type C<TYPE>, such as "HASH", 1N/A"ARRAY", or "Regexp". 1N/A=item C<< $obj->can( METHOD ) >> 1N/A=item C<< CLASS->can( METHOD ) >> 1N/A=item C<can( VAL, METHOD )> 1N/AC<can> checks if the object or class has a method called C<METHOD>. If it does 1N/Athen a reference to the sub is returned. If it does not then I<undef> is 1N/Areturned. This includes methods inherited or imported by C<$obj>, C<CLASS>, or 1N/AC<can> cannot know whether an object will be able to provide a method 1N/Athrough AUTOLOAD, so a return value of I<undef> does not necessarily mean 1N/Athe object will not be able to handle the method call. To get around 1N/Athis some module authors use a forward declaration (see L<perlsub>) 1N/Afor methods they will handle via AUTOLOAD. For such 'dummy' subs, C<can> 1N/Awill still return a code reference, which, when called, will fall through 1N/Ato the AUTOLOAD. If no suitable AUTOLOAD is provided, calling the coderef 1N/AC<can> can be called as a class (static) method, an object method, or a 1N/AWhen used as a function, if C<VAL> is a blessed reference or package name which 1N/Ahas a method called C<METHOD>, C<can> returns a reference to the subroutine. 1N/AIf C<VAL> is not a blessed reference, or if it does not have a method 1N/AC<METHOD>, I<undef> is returned. 1N/A=item C<VERSION ( [ REQUIRE ] )> 1N/AC<VERSION> will return the value of the variable C<$VERSION> in the 1N/Apackage the object is blessed into. If C<REQUIRE> is given then 1N/Ait will do a comparison and die if the package version is not 1N/Agreater than or equal to C<REQUIRE>. 1N/AC<VERSION> can be called as either a class (static) method, an object 1N/Amethod or a function. 1N/AYou may request the import of all three functions (C<isa>, C<can>, and 1N/AC<VERSION>), however it isn't usually necessary to do so. Perl magically 1N/Amakes these functions act as methods on all objects. The one exception is 1N/AC<isa>, which is useful as a function when operating on non-blessed