Implicit inheritance in Perl

Implicit inheritance in Perl Implicit inheritance
Today, I saw a disconnection. Code :

A. PM

Code: [copy to clipboard] Package;

...

Sub test {
Print "test \ n ";
}

B. PM

Code: [copy to clipboard] Package B;
Use;

B-> test ();

I think it is strange that B does not explicitly inherit from A. Why can I use the test function of?

Finally, we found that the import function was rewritten in A. PM.

Code: [copy to clipboard] sub import {
My $ class =$ _ [0];
My $ caller = caller (0 );
Unless ($ caller-> ISA ('A ')){

No strict 'refs ';
Print "importing a \ n ";
Push @ {"$ caller \: ISA"}, $ class;

}

}

Caller refers to the call stack. Caller (0) is the top package name. Because B calls the import of A, it is 'B'
B: ISA is the parent class array.