Ways to modify the Perl syntax. Ways to implement internal DSLs and external DSLs in Perl.

Underlying mechanisms

Lexer level

[external DSLs]

• source filters — considered fairly unsafe
• PL_keyword_plugin
• perlapi.pod#Lexer-interface

Parser level

• parser functions were added in Perl v5.14.0
• B::Hooks::Parser

Opcode level

• PL_check
  • Devel::Declare
• B::Hooks::OP::PPAddr (backlinks)
• MAGIC [Variable::Magic]
• tools that can't be triggered directly by the end-programmer, but are instead triggered by other tools mentioned above
  • custom opcodes [OP_CUSTOM]
  • B::Generate (often used within a CHECK {...} block)

Other ways of modifying behavior

• operator overloading
• overriding builtin functions

Modules that build on those mechanisms to do macro-like stuff

• subs::auto
• Code::Splice
• Devel::Declare::Macro (as-yet unreleased)
• Macro
• fairly language-bendy, but maybe not as powerful as macro-like things
  • PerlX::QuoteOperator
  • PerlX::MethodCallWithBlock

TODO

• cpan_grep for all modules that use any of the lexer APIs
• cpan_grep for all modules that use any of the parser APIs