sub infinite_evens {
    my $curr = shift;
    $curr++ if $curr % 2;
    my $next;
    return sub {
        if ( ! defined $next ) { return $next = $curr }
        return $next += 2;
    };
}
my $next_even = infinite_evens( 41 );
print $next_even->(), "\n" while 1;