what is the difference between parent and @ISA?

Question

both parent and @ISA doing same working, what is use of parent and @ISA accordingly.

package Baz;
    use parent qw(Foo Bar);

or

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

Answer 1

use parent is simply a concise way of doing a require and pushing the package name onto @ISA in one statement. It happens at compile time instead of a simple our @ISA = qw/ Foo Bar / which is done at run time, and means you have to code the package name only once which may reduce errors. It will also raise a warning if a package tries to inherit from a package of the same name, which would be useless and could cause an infinite inheritance loop.

In short, use parent is a more concise and easy way to get everything right.

Answer 2

parent is syntactic sugar to set a package's @ISA variable and automatically load its superclasses at compile time. As the parent documentation states, there is no functional difference between the two code blocks in the OP.