Using a package does just that, it uses it. However using base , uses the package and adds it to the @ISA so that it the packages are inherited.

From the documentation:

package Baz;
use base qw(Foo Bar);
[download]

Is equal to

package Baz;
BEGIN {
    require Foo;
    require Bar;
    push @ISA, qw(Foo Bar);
}
[download]

Edit by castaway: Closed small tag in signature