Mozilla Sweet.js: Extending JavaScript with Macros

Perl6 also has a macro keyword for creating hygienic macros - http://en.wikipedia.org/wiki/Perl_6#Macros

For Perl5 you can use Devel::Declare (https://metacpan.org/module/Devel::Declare) or Devel::CallParser (https://metacpan.org/module/Devel::CallParser) to achieve macro like effects.

For eg. Here's the Sweet.js def add macro using Devel::Declare...

  package MyDef;
  use strict;
  use warnings;
  use base 'Devel::Declare::MethodInstaller::Simple';
   
  sub import {
      my $class  = shift;
      my $caller = caller;
      my $arg    = shift;
   
      $class->install_methodhandler(
          into => $caller,
          name => 'def',
      );
  }
  
  sub parse_proto {
      my $ctx = shift;
      my ($proto) = @_;
      "my ($proto) = \@_;";
  }
  
  1;

Then...

  use 5.016;
  use warnings;
  use MyDef;

  def add ($x, $y) { $x + $y }

  say add(1, 2);   # => 3

So when the compiler sees the def keyword then MyDef takes over and converts the line into...

  sub add { my ($x, $y) = @_; $x + $y }

... then passes everything back to the perl parser to continue compiling the rest of the code.

Adds what to http://news.ycombinator.com/item?id=4650929?

This seems to be blatantly plagiarised from somewhere, although I can't remember quite where.

Exactly why and how does this let me do stuff I couldn't do before with JS? The example used here looks like something that could be done just as easily with OOP at first glance...