The Want module is quite interesting, but seems a little awkward in terms of implementation. Here's an example: 
use Want;

sub fooz : lvalue
{
     defined ($foo_new)?
        $foo_new
        : (want('LVALUE','ASSIGN')?
              $foo_new = $foo
              : $foo);
}

[download]
Internally, there is a function from the Wait.xs component called 'want_lvalue', which is really all I need. If it were assigned a default parameter value (it relates to stack depth) then it could be used like so: 
use Want;

sub fooz : lvalue
{
     defined ($foo_new)?
        $foo_new
        : want_lvalue?
              $foo_new = $foo
              : $foo);
}

[download]
This does seem to be a lot neater, though not currently implemented.

It just goes to show that CPAN has a module for every occasion. I wouldn't be surprised to see Cheese::Grater.

Thanks for the tip. It's exactly what I was looking for.

In reply to Re^2: Side Context in an 'lvalue' Subroutine by tadman
in thread Side Context in an 'lvalue' Subroutine by tadman

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