How 'bout:

#!/usr/bin/perl -w

### set up some packages
### this would normally be done using their own files
{
  package Nifty;
  sub new {
    my $type = shift;
    my $self = {@_};
    if( $self->{type} ){
#     require $self->{type}; # if the Nifty::A packages
      # were in their own files
      $type = $self->{type};
    }
    return bless( $self, $type);
  }

  sub get {
    return "Some_Value";
  }
  ### default print method
  sub print_it {
    my $self = shift;
    my $str  = shift;
    return $str;
  }
}

{
  package Nifty::A;
  @Nifty::A::ISA = qw(Nifty);
  sub print_it {
    my $self = shift;
    my $str  = shift;
    return "<a href=$str>$str</a>";
  }
}

{
  package Nifty::B;
  @Nifty::B::ISA = qw(Nifty);
  sub print_it {
    my $self = shift;
    my $str  = shift;
    return uc($str);
  }
}

# more types et cetera

### here is the main program
use strict;

my ($obj,$val);

$obj = Nifty->new();
$val = $obj->get();
print $obj->print_it( $val ) ,"\n";

$obj = Nifty->new(type=>'Nifty::A');
$val = $obj->get();
print $obj->print_it( $val ) ,"\n";

$obj = Nifty->new(type=>'Nifty::B');
$val = $obj->get();
print $obj->print_it( $val ) ,"\n";

exit;
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Basically, put the normal functionality in the base class. Anything that changes, put in the sub classes.

my @a=qw(random brilliant braindead); print $a[rand(@a)];