Closures

10. An anonymous subroutine that grabs lexical variables from its containing environment is a closure. Remember that it does not just take a snapshot of the value at the instant the anonymous subroutine is seen.

    # declare an anonymous subroutine, and return a reference to it. my $foo = 10; $rs = sub {
     print "Foo is $foo\n"; # Grabs $foo };
     &$rs(); # Call the closure through the reference 
    

11. The closure keeps the grabbed variable's value around even when the variable goes out of scope.

    sub init_counter {
     my $num = shift; # lexical variable to be grabbed $rs = sub {
     print $num++," ";
    };
     return $rs;
    }
    $rs_counter = init_counter(10); # $rs_counter is a ref-to-sub for (1..5) {&$rs_counter()};
     # Prints 10 through 14