Alternatively, you can wrap the class code in a BEGIN block. That will ensure that your classes are initialized before the main code gets run. You don't need "require" or '1;' when the code is in the same file. Also, 'use strict' is lexically scoped, so you really only need to say it at the top.

#!/usr/bin/perl
use strict;
use warnings;

my $a = B->new();

BEGIN {

    package A;

    sub new {
        my ( $class, %args ) = @_;
        my $self = bless {}, ref($class) || $class;
        return $self;
    }

    package B;

    @B::ISA = qw(A);

    sub _init {
        my ( $self, %args ) = @_;
        $self->{_title} = $args{title} || undef;
    }

}
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Thank you!