You need to alter the behavior of the sub. The derived class code looks like:

package MyChild;
use strict;
use vars qw/@ISA/;
@ISA = qw/MyMother/;

sub new {
   my ($class, @args) = @_;
   my $self = $class->SUPER::new(@args);
   bless $self, $class;
   $self;
}

sub modified {
    return 0 if $_[0]->{TYPE} == 1;

    $_[0]->SUPER::modified ();
}
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and the test code then prints:

1
0
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