#!/usr/bin/perl  -w
use strict;
use feature ':5.10';

# note use of BEGIN and 'caller' to achieve macro definition...


BEGIN {
	sub class_vars {
		my $pck=caller;
		foreach(@_) {
			eval "
			my \$p=\"__PACKAGE__\";
			package ${pck};
			our \$$_;
			sub ${pck}::$_ {
				shift;
				\$$_ = \$_[0] if \@_;
				\$$_;
			}
			package \$p;
			"
		}
	}
}


package MyPackage;
	*class_vars=\&main::class_vars;
{

	class_vars( qw(one two three) );

  sub init_one_from_three {
		$one=$three-2;
	}

	sub new {
		my $package=shift;
		my $parms=$_[0];
		
		my $this={};

		foreach(keys %$parms) {
			$$_=$parms->{$_};
		}

		bless $this, $package;
	}
}

package main;

my $p=new MyPackage({three => 3,});

$p->two(1);
$p->init_one_from_three;

printf "two=%d, three=%d, one=%d\n",$p->two, $p->three, $p->one;