NAME

overload::eval - Hooks the native string eval() function

SYNOPSIS

As a command line tool:

  uneval obfuscated.pl

As a module:

  use overload::eval 'my_callback';
  sub my_callback { print and eval for $_[0] }

  sub rot13 {
      local $_ = shift;
      tr[A-Za-z][N-ZA-Mn-za-m];
      return $_;
  }
  eval(rot13());

DESCRIPTION

This module hooks the native eval() function and sends it to your function instead. The eval() function operates normally within your function.

This module requires user pragmas which are a feature present only in 5.9.4+.

Using this module is simplicity itself. If you've declared the hook, any uses of string eval in that lexical scope are going to be redirected to the function you named.

  {
      use overload::eval;
      eval '...';
  }
  sub eval {
      # eval goes here
  }

If you declare a hook name, execution is redirected to that named function instead of eval.

  {
      use overload::eval 'hook';
      eval '...';
  }
  sub hook {
      # eval goes here because we declared 'hook'
  }

BUILTIN-HOOKS

There are some built-in hooks. They are accessed by importing them by name. This can also be done on the command line.

-p

-print

The -print option prints the source code of the eval() and then exits the program. I expect this option is most useful when untangling obfuscated programs. Use of this option changes the pragma so it operates globally. All evals are now hooked.

-p is a synonym for -print.

The program:

  perl -Moverload::eval=-p obfuscated.pl

when run on:

  $_='cevag "Uryyb jbeyq!\a"';tr/A-Za-z/N-ZA-Mn-za-m/;eval;

prints the following and exits:

  print "Hello world!\n"

-pe

-print-eval

The -print-eval option prints the source code of the eval() before running it. Use of this option changes the pragma so it operates globally. All evals are now hooked.

-pe is a synonym for -print-eval.

The program:

  perl -Moverload::eval=-print-eval obfuscated.pl

when run on:

  $_='cevag "Uryyb jbeyq!\a"';tr/A-Za-z/N-ZA-Mn-za-m/;eval;

prints the following:

  print "Hello world!\n"

and then runs the code which prints:

  Hello world!

DISPELLING MAGIC

This module overloads eval() only with the lexical scope you've requested. To avoid triggering this module, either create a new lexical scope or just disable the overloading.

  {
    use overload::eval;
    eval '...'; # Overloaded;
  }
  eval '...'; # NOT overloaded

Or...

  use overload::eval;
  eval '...'; # Overloaded;
  
  no overload::eval;
  eval '...'; # NOT overloaded.

CAVEATS

This module does not overload the block form of eval. Sorry. That's an entirely different kind of technology.

  eval { ... };

AUTHOR

Josh Jore - jjore@cpan.org

LICENSE

This module is available under the same licences as perl, the Artistic license and the GPL.