package Child;
use base qw(Parent);
sub new {
    my $class = shift;
    my $self = $class->SUPER::new(); # call superclass' constructor with provided classname
    $self->do_child_specific_stuff();
    return $self;
}

##</code><code>##

# ...
  my $self = $class->SUPER::new();
  bless $self,$class;  # re-bless to right classname
  $self->do_child_specific_stuff();
# ...