I'm asking as a point of learning here. I have a simple module that takes a key/value pair, stores it, then lets the user access it. Basically, a hash but as a module. Why? Just so I can try different things out.

The question is about naming methods in the module the same as Perl's built-in functions. For example, since I am storing key/value pairs I want to know if a key exists. Perl has a built-in function exists() and has to be called on an array or hash, e.g. exists(foo[0])

That name "exists" is the perfect description of what I want to do with this module. So if I write in the module:

sub exists {
  ... blah ...
}
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I can call it without issue like this:

use MyPackage;
my $obj = MyPackage->new();
$obj->set_value('foo', 'bar');
if($obj->exists('foo')) {
    print "that key is there\n";
}
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It works just fine. So I want to know why I'm able to override the built-in function? Is it because the procedure I'm writing is always called by the object handle? Does that make it NOT the same as the built-in function?

Just trying to understand how it works