Syntax::Feature::Sugar::Callbacks - Add sugar for declarative method

    version 0.002

        use AnythingExportingMethodModifiers;
        use syntax 'sugar/callbacks' => {
            -callbacks => {
                after   => {},
                before  => {},
                around  => { -before => ['$orig'] },

        after  foo ($n) { $self->something($n) }
        before bar ($n) { $self->something($n) }
        around baz ($n) { $self->something($self->$orig($n)) }

    You probably won't use this extension directly. That's why it doesn't
    even have an "import" method. Its main reasoning is the ability to
    provide on-the-fly sugar for method declarators, most commonly "before",
    "after" and "around". This extension will directly dispatch to the
    original subroutine, and requires these to be setup before-hand.
    Currently, all callbacks will first receive the name of the declared
    method, followed by the code reference.

    Note that no cleanup of the original handlers will be performed. This is
    up to the exporting library or the user.

        $class->install( %arguments )

    Called by syntax (or others) to install this extension into a namespace.

    All declarations must currently be in one of the forms

        <keyword> <name> (<signature>) { <body> }
        <keyword> <name> { <body> }

    The "keyword" is the name of the declared callback. The "name" can
    either be an identifier like you'd give to "sub", or a double-quoted
    string if you want the name to be dynamic:

        after "$name" ($arg) { ... }

    The signature, if specified, should be in one of the following forms:

        ($foo, $bar)
        ($class: $foo, $bar)

    Variables before ":" will be used as replacement for the invocant.
    Parameters specified via "-before" and "-middle" will always be

    The statement will automatically terminate after the block. The return
    value will be whatever the original callback returns.

    You can supply subroutine attributes right before the block.

    Defaults to $self, but you might want to change this for very
    specialized classes.

    This is the set of callbacks that should be setup. It should be a hash
    reference using callback names as keys and hash references of options as
    values. Possible per-callback options are

        An array reference of variable names that come before the invocant.
        A typical example would be the original code reference in "around"
        method modifiers.

        An array reference of variable names that come after the invocants,
        but before the parameters specified in the signature. Use this if
        the code reference declared with the construct will receive a
        constant parameter. There is no current way to override this in the
        signature on a per-construct basis.

        An array reference of variable names that are used when no signature
        was provided. An empty signature will not lead to the defaults being

        By default, anonymous constructs will not automatically terminate
        the statement after the code block. If this option is set to a true
        value, all uses of the construct will be terminated.

        If set to a true value, anonymous versions of this construct can be
        declared. If no name was specified, only the code reference will be
        passed on to the callback.

        If set to a true value, a name will not be expected after the
        keyword and before the signature.

    *   syntax

    *   Devel::Declare

    Please report any bugs or feature requests to or through the web
    interface at:

    Robert 'phaylon' Sedlacek <>

    This software is copyright (c) 2011 by Robert 'phaylon' Sedlacek.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.