base - Establish IS-A relationship with base class at compile time
    package Baz;
    use base qw(Foo Bar);
Roughly similar in effect to
    BEGIN {
        require Foo;
        require Bar;
        push @ISA, qw(Foo Bar);
    }
Will also initialize the %FIELDS hash if one of the base
classes has it. Multiple inheritance of %FIELDS is not
supported. The 'base' pragma will croak if multiple base classes has a
%FIELDS hash. See
the fields manpage for a description of this feature.
When strict 'vars' is in scope base also let you assign to @ISA without having to declare
@ISA with the 'vars' pragma first.
This module was introduced with Perl 5.004_04.