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NAME

UNIVERSAL - base class for ALL classes (blessed references)


SYNOPSIS

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

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


DESCRIPTION

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 TYPE or 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 does then a reference to the sub is returned. If it does not then undef is 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 the package the object is blessed into. If REQUIRE is given then it will do a comparison and die if the package version is not greater 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 either of the following statements is true.

VAL is a blessed reference and is blessed into package TYPE or 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 not a 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.


DISCLAIMER

We are painfully aware that these documents may contain incorrect links and misformatted HTML. Such bugs lie in the automatic translation process that automatically created the hundreds and hundreds of separate documents that you find here. Please do not report link or formatting bugs, because we cannot fix per-document problems. The only bug reports that will help us are those that supply working patches to the installhtml or pod2html programs, or to the Pod::HTML module itself, for which I and the entire Perl community will shower you with thanks and praises.

If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.

--Tom Christiansen, Perl Documentation Compiler and Editor


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