with minimal changes(blue parts) to your initial code

package Bar;
use Data::Dumper;
use Moose;

sub bar
{
    my $arg = shift;
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    if(ref($arg) eq 'ARRAY') {
        return map {
            $_->bar;
        } @{ $arg };
    }
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    print "bar\n";
}

package Foo;

use Moose;


sub foo
{
    return [(Bar->new)x3]; # what magic do i need to apply here?
}

package main;
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use autobox ARRAY => 'Bar';
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Foo->new->foo->bar; 
#no more "Can't call method "bar" on unblessed reference"
#because now ->bar is a native method of ARRAYREFs.
#actually all the methods of Bar are native methods on ARRAYREFs now.
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