Given:

use warnings;
use strict;

package Frobnicate::Bar;

sub new {
    my ($class) = @_;
    return bless {}, $class;
}


sub sayWhat {
    my ($self) = @_;
    
    if (ref $self) {
        print "I'm a ", ref $self, " method\n";
    } else {
        print "I'm a ", __PACKAGE__, " function\n";
    }
}


package Frobnicate::Foo;

our @ISA = qw/Frobnicate/;

sub new {
    my ($class) = @_;
    return Frobnicate::new ($class);
}


sub sayWhat {
    my ($self) = @_;
    
    if (ref $self) {
        print "I'm a ", ref $self, " method\n";
    } else {
        print "I'm a ", __PACKAGE__, " function\n";
    }
}


package Frobnicate;


sub new {
    my ($class) = @_;
    return bless {}, $class;
}


sub sayWhat {
    my ($self) = @_;
    
    if (ref $self) {
        print "I'm a ", ref $self, " method\n";
    } else {
        print "I'm a ", __PACKAGE__, " function\n";
    }
}


1;
[download]

consider:

use strict;
use warnings;
use noname1;

Frobnicate::Bar->new ()->sayWhat ();
Frobnicate::Foo->new ()->sayWhat ();
Frobnicate->new ()->sayWhat ();
Frobnicate::Bar::sayWhat ();
Frobnicate::Foo::sayWhat ();
Frobnicate::sayWhat ();
[download]

which prints:

I'm a Frobnicate::Bar method
I'm a Frobnicate::Foo method
I'm a Frobnicate method
I'm a Frobnicate::Bar function
I'm a Frobnicate::Foo function
I'm a Frobnicate function
[download]

So, exactly what is hidden from the calling code exactly?

btw, I don't condone the use of the same sub as a method and a function. Used here to reduce code peripheral to the main thesis.