use strict;
use warnings;

package My;

sub new {
    my ($class) = @_;
    return bless {}, $class;
    }

sub ext_show {
    my ($self, $name) = @_;
    print "Hello $name!\n";
    return 1;
    }

package main;

my $A = 'My'->new();
my $method = 'ext_' . shift;

$A->$method(@ARGV);

##</code><code>##

Hello Bob!