Naming a package 0 is a fatal, compilation error ... The problem is likely to occur where, in some code completely separate from yours, someone writes '$x->your_method()' when, perhaps, '$y->your_method()' was intended.

Another example might be auto-generated package names (though if such code generated a package named "0", one could question the sanity of that choice...)

use warnings;
use strict;

{ package Foo;
    use Data::Dump;
    use Scalar::Util qw/blessed/;
    sub new { return bless {}, shift }
    sub foo {
        my $self = shift if blessed($_[0]) && $_[0]->isa(__PACKAGE__);
        dd 'foo', $self, \@_;
    }
    sub bar {
        my $self = shift if defined blessed($_[0])
            && $_[0]->isa(__PACKAGE__);
        dd 'bar', $self, \@_;
    }
}

{ no strict 'refs'; @{"0::ISA"} = ('Foo') }

my $x = bless {}, '0';
$x->foo();  # ("foo", undef, ["0=HASH(0x561239194f3e)"])
$x->bar();  # ("bar", "0=HASH(0x561239194f3e)", [])

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In reply to Re^5: Calling module function from within a blessed module by haukex
in thread Calling module function from within a blessed module by Bod

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