I should have mentioned it in the main post, but I wanted to avoid eval for several reasons:

1. There is a pretty hefty performance penalty when doing string eval
2. What do I do with syntax errors? If I'm stitching subrefs, I know they compile.
3. How do I stitch closures together?

The impetus for this was this syntax:

class Foo => {
    class_method 'c_foo' =>
        signature (Int, Num(5)),
        body => { ... };

    method 'foo' =>
        signature (Any, Hash),
        returns ( Int ),
        body => { ... };
};

Foo->add_post_process(
    methods => 1,
    class_methods => 0,
    action => sub { ... },
);
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The idea being that you first have a check for if the referent is a class name or a blessed reference into that class. Then, you have a check on the parameters being passed in. All of these are really easily done as closures. Except, now every single method call has some 10-40 subroutines that stack 2-3 above the body of the method which, itself, is stacked. That's a massive performance penalty, plus it makes debugging errors extremely difficult.