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PPI::Token::Prototype(3pm) User Contributed Perl Documentation PPI::Token::Prototype(3pm)


PPI::Token::Prototype - A subroutine prototype descriptor


  isa PPI::Token
      isa PPI::Element


  sub ($@) prototype;


Although it sort of looks like a list or condition, a subroutine prototype is a lot more like a string. Its job is to provide hints to the perl compiler on what type of arguments a particular subroutine expects, which the compiler uses to validate parameters at compile-time, and allows programmers to use the functions without explicit parameter parens.

Due to the rise of OO Perl coding, which ignores these prototypes, they are most often used to allow for constant-like things, and to "extend" the language and create things that act like keywords and core functions.

  # Create something that acts like a constant
  sub MYCONSTANT () { 10 }
  # Create the "any" core-looking function
  sub any (&@) { ... }
  if ( any { $_->cute } @babies ) {


This class provides one additional method beyond those defined by the PPI::Token and PPI::Element parent classes.


The "prototype" accessor returns the actual prototype pattern, stripped of flanking parens and of all whitespace. This mirrors the behavior of the Perl "prototype" builtin function.

Note that stripping parens and whitespace means that the return of "prototype" can be an empty string.


See the support section in the main module.


Adam Kennedy <>


Copyright 2001 - 2011 Adam Kennedy.

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

The full text of the license can be found in the LICENSE file included with this module.

2022-07-23 perl v5.34.0