closure.cpp

// Compile with:
//
//    g++ -W -Wall -Wextra -pedantic -std=c++0x closure.cpp -o closure

#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <memory>
#include <initializer_list>

class Container {
private:
	std::vector<int>	*_v;

public:
	const std::vector< int > & operator()( const int & ref ){
		if( ref % 2 == 0 ){
			(*_v).push_back( ref );
		}
		return *_v;
	};

	const std::vector< int > & operator()(){
		return (*_v);
	};
	
	Container() : _v( new std::vector<int> ) {
	};

	virtual ~Container(){
		// Yes, this is an intentional memory leak for
		// sake of brevity
	}
};

int main( void ){

	Container *visitor = new Container();

	auto array = {
		1,2,3,
		4,5,6,
		7,8,9,
		10,11,12,
		13,14,15,
		16,17,18
	};

	// Add all even elements to the closure "visitor"
	std::for_each( array.begin(), array.end(), *visitor );

	// Print them out, using lambda functions
	std::for_each( (*visitor)().begin(), (*visitor)().end(), []( const int & ref ){
		std::cout << ref << std::endl;
	});

	delete visitor;

	return 0;
}

closure.pl

#!/usr/bin/perl -w
use strict;

sub closure {
	my @a;

	return ( sub {
		my $v = shift;
		push( @a, $v )
			if $v % 2 == 0 and ( $v =~ /^\d+$/ );
	}, \@a );
}

my ($visitor, $aref) = closure();

&$visitor($_) for 1..18;

print join( "\n", @$aref ),"\n";

Makefile

closure:	closure.cpp
	g++ -W -Wall -Wextra -pedantic -std=c++0x closure.cpp -o closure

clean:
	rm closure