#!/usr/bin/perl -w
use strict;
print "Content-type: text/plain\n\n";

sub outer {
 my ($a) = @_;
 my $b = "sophie";
 my $d = "sam";

 print "at start of outer: \n";
 print "    a = '$a' \n";

 # This is a closure - a reference to an anonymous code block.
 # It has access to all the lexical variables in scope at 
 # the moment of its definition.
 my $innerFunc = sub { 
		      print " -- innerFunc \n";
	              print "     a is '$a' \n";  
	              print "     b is '$b' \n";  
	              print "     passed in: ", @_, "\n";
		      print "     this copy of d is '$d' \n";

                      $a = $a . " - modified";
	              $d = $d . " - changed";

                     };

 # The loop variable $d in this for loop doesn't behave 
 # the way I expected.  Apparently, to keep the value 
 # (i.e. 'sam') undisturbed when the loop exists, the "foreach"
 # creates another scalar value, and points $d at that new scalar
 # value while the loop is running.  Then at the end, it points $d
 # back at the original value.  But the value of $d within the 
 # closure still refers to the original, "real" value - it doesn't
 # see the "one", "two", "three" we're looping over.
 
 foreach $d ( qw( one two three) ) {

    my $c = $d . "ish";
    $b = $c x 2;

    print " getting ready to call inner - within loop, d = '$d' \n";
    $innerFunc->( $c );

    print "\n";
 }

 print " back in outer, outside loop : \n";
 print "     a is '$a' \n";
 print "     b is '$b' \n";
 print "     d is '$d' \n";

}

outer( "Tom" );