The trick here is to return a closure from a generator function. Below is a complete working example. However the salient bit is returning refs to $cont and $foo from the generator function, and dereferencing them in the caller to initialize or change them.

    package Foobar;

    sub _setup_xforms {
        my ($cont, $foo);
        return (\$cont, \$foo, {
            xform1 => sub { printf("Level %d,foo=%s\n", $cont, $foo); 
+},
        });
    };

    sub transform {
        my ($self, $cont) = @_;

        my ($cont_ref, $foo_ref, $xforms) = _setup_xforms();

        $$cont_ref //= $cont; # //= to convince you it's not still set
       
        for my $xform (values %$xforms) {
            $$foo_ref //= 0; # //= as above 
            $xform->();
            $$foo_ref++;
            $self->transform($cont + 1) if ($cont < 5);
            print "Level $cont done, foo=$$foo_ref\n";
        }
    }
    
    sub new { bless({},'Foobar') }


    my $foo = new Foobar( id => 1 );

    $foo->transform(0);

[download]

This produces the following output:

    Level 0,foo=0
    Level 1,foo=0
    Level 2,foo=0
    Level 3,foo=0
    Level 4,foo=0
    Level 5,foo=0
    Level 5 done, foo=1
    Level 4 done, foo=1
    Level 3 done, foo=1
    Level 2 done, foo=1
    Level 1 done, foo=1
    Level 0 done, foo=1

[download]

In reply to Re: Perl OO: Need a concise way of representing operations on an object by rjt
in thread Perl OO: Need a concise way of representing operations on an object by wanna_code_perl

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