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 perlobj
UNIVERSAL
UNIVERSAL provides the following methods
isa returns true if REF is blessed into package TYPE or inherits from package TYPE.
isa
REF
TYPE
isa can be called as either a static or object method call.
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
METHOD
can can be called as either a static or object method call.
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
$VERSION
REQUIRE
VERSION can be called as either a static or object method call.
The isa and can methods can also be called as subroutines
isa returns true if one of the following statements is true.
VAL is a reference blessed into either package TYPE or a package which inherits from package TYPE.
VAL
VAL is a reference to a TYPE of Perl variable (e.g. 'HASH').
VAL is the name of a package that inherits from (or is itself) package TYPE.
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
use UNIVERSAL qw(...)
*isa = \&UNIVERSAL::isa;
to import isa into your package.
To install Env, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Env
CPAN shell
perl -MCPAN -e shell install Env
For more information on module installation, please visit the detailed CPAN module installation guide.