MAN page from Old RedHat 5.X perl-5.004-4.i386.rpm

UNIVERSAL

Section: Perl Programmers Reference Guide (3)
Updated: perl 5.004, patch 04
Index

NAME

UNIVERSAL - base class for ALL classes (blessed references)

    $io = $fd->isa("IO::Handle");    $sub = $obj->can('print');

    $yes = UNIVERSAL::isa($ref, "HASH");

UNIVERSAL is the base class which all bless references will inherit from,see the perlobj manpage

UNIVERSAL provides the following methods

isa ( TYPE ): isa returns true if REF is blessed into package TYPEor inherits from package TYPE.
isa can be called as either a static or object method call.
can ( METHOD ): can checks if the object has a method called METHOD. If it doesthen a reference to the sub is returned. If it does not then undefis returned.
can can be called as either a static or object method call.
VERSION ( [ REQUIRE ] ): VERSION will return the value of the variable $VERSION in thepackage the object is blessed into. If REQUIRE is given thenit will do a comparison and die if the package version is notgreater than or equal to REQUIRE.
VERSION can be called as either a static or object method call.

The isa and can methods can also be called as subroutines

UNIVERSAL::isa ( VAL, TYPE ): isa returns true if the first argument is a reference and eitherof the following statements is true.
: VAL is a blessed reference and is blessed into package TYPEor inherits from package TYPE
: VAL is a reference to a TYPE of perl variable (er `HASH')
UNIVERSAL::can ( VAL, METHOD ): If VAL is a blessed reference which has a method called METHOD,can returns a reference to the subroutine. If VAL is nota blessed reference, or if it does not have a method METHOD,undef is returned.

These subroutines should not be imported via use UNIVERSAL qw(...).If you want simple local access to them you can do

  *isa = \&UNIVERSAL::isa;

to import isa into your package.

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