NAME

       "Sublike::Extended" - enable extended features when parsing "sub"-like syntax

SYNOPSIS

          use v5.26;
          use Sublike::Extended;
          use experimental 'signatures';

          extended sub greet (:$name = "world") {
             say "Hello, $name";
          }

          greet( name => $ENV{USER} );

DESCRIPTION

       This module extends the syntax for declaring named or anonymous subroutines using Perl's builtin "sub"
       keyword, or other similar keywords provided by third-party modules, to enable parsing of extra features.

       Currently, the only extended features that are provided are related to the parsing of a subroutine
       signature. Since signatures are only available on Perl version 5.26 or later, this module is unlikely to
       be useful in earlier versions of Perl.

   Named parameters
       Extended subroutines can be declare named parameters in the signature, after any positional ones. These
       take the form of a name prefixed by a colon character. The caller of such a function should pass values
       for these parameters by the usual name-value pair syntax that would be used for passing into a regular
       hash. Within the body of the subroutine the values passed into these are unpacked into regular lexical
       variables.

          extended sub colour (:$red, :$green, :$blue) {
             ... # $red, $green and $blue are available as regular lexicals
          }

          # argument order at the caller site is not important
          colour(green => 1, blue => 2, red => 3);

       As with positional parameters, they are normally mandatory, but can be made optional by supplying a
       defaulting expression. If the caller fails to pass a value corresponding to the parameter, the default
       expression is evaluated and used instead.

          extended sub f (:$x0, :$x1, :$x2 = 0) { ... }
          # The caller must provide x0 and x1, but x2 is optional

       An optional slurpy hash is also permitted after all of these. It will contain the values of any other
       name-value pairs given by the caller, after those corresponding to named parameters have already been
       extracted.

          extended sub g (:$alpha, :$beta, %rest) { ... }

   Parameter Attributes
       Parameters to extended subroutines can use attribute syntax to apply extra attributes to individual
       parameters.

          extended sub info ($x :Attribute) { ... }

       Any attributes that are available are ones that have been previously registered with XS::Parse::Sublike
       using its XS-level API. The particular behaviour of such an attribute would be defined by whatever module
       provided the attribute.

KEYWORDS

   extended
          extended sub NAME (SIGNATURE...) { BODY... }

          extended sub (SIGNATURE...) { BODY... };

       This prefix keyword enables extra parsing features when handling a "sub" (or other sub-like function
       keyword).

       This keyword can be freely mixed with other "sub"-prefix keywords, such as "async" from
       Future::AsyncAwait

          async extended sub f (:$param) { ... }

       This can also be used with other keywords that provide "sub"-like syntax, such as "method" from
       Object::Pad or the core "use feature 'class'".

          extended method f (:$param) { ... }

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>

perl v5.38.2                                       2024-03-31                             Sublike::Extended(3pm)