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Why does it need parentheses for some built in functions but not for others? #111

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anonyno opened this issue Oct 27, 2020 · 2 comments
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Why does it need parentheses for some built in functions but not for others? #111

anonyno opened this issue Oct 27, 2020 · 2 comments
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@anonyno
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anonyno commented Oct 27, 2020

maybe i just don't understand Perl but why is print; okay but not die;. i need to use die(); for it not to complain.

Also print 'example' is okay even though "All subroutines must use parentheses".
@xsawyerx xsawyerx added the bug label Jan 30, 2021
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maybe i just don't understand Perl but why is print; okay but not die;. i need to use die(); for it not to complain.

This is indeed a bug. I've marked this ticket as such.

Also print 'example' is okay even though "All subroutines must use parentheses".

print (and die) are not "subroutines," they are "keywords." Keywords are the reserved barewords provided by the language, also referred to as "builtins" or "builtin functions." They do not need parenthesis by default because we are aware of their parsing rules.

User-created functions ("subroutines") require parenthesis so we can adequately figure out how to lex and parse them. Subroutine prototypes allow the user to give the perl lexer additional parsing rules so it can avoid parenthesis but that makes it very difficult to statically parse because you need to go into compilation mode to introduce these new prototypes and understand them. This is why Guacamole doesn't support subroutine prototypes and requires all subroutines (user-provided functions) to include parenthesis.

xsawyerx added a commit that referenced this issue May 30, 2022
@xsawyerx
GH #111: Support die;
e2e9150
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die is now supported.

xsawyerx added a commit that referenced this issue Jun 20, 2022
@xsawyerx
v0.008
2838253 
    * GH #23: (VERY) Preliminary support for extending the grammar.
    * GH #111: Support "die".
    * GH #112: Support "readline STDIN" or "readline(STDIN)".
    * GH #113: Support "$#_" (but not "$# _").
    * GH #114: Support all forms of binmode() (Val @valcomm).
    * GH #115: Support all forms of for() loop (Val @valcomm).
    * RT #132920: Fix confusion of quote-like operators by comments.
    * Support "_" in file operations ("-x _", etc.).
    * Support "$foo->$bar" and "$foo->$_".
    * Support 'eval "..."' or 'eval $foo'.
    * Improve wording on top-level anonymous hashes.
    * When failing without an exception, we throw an exception with
      more information (e.g., "print _").
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@xsawyerx @anonyno