#!/usr/bin/perl

use Benchmark 'timethese';

$rCODE = reverse ($CODE = << 'END');
<this is a sample program> int x = 10;
<what a silly grammar> str y = "cool \" beans";
if (len(y) GREATER_THAN x) { <can't use gt and lt symbols... heehee>
  <empty comment coming up>
  print y, " is longer than ", x, " characters";
  <>
  <and more stuff to come soon>
  chop(y,x);
  print "I sliced 'y' down to ", x, " characters for you";
}
END

    ($last) = $CODE =~ m{
      \A
      (?: <[^<>]*> | " [^"\\]* (?: \\. [^"\\]* )* " | (?>[^"<>]*) )*
      (<[^<>]*>)
      (?: " [^"\\]* (?: \\. [^"\\]* )* " | (?>[^"<>]*) )*
      \z
    }x;
    print "forwards: $last\n";

    $last = scalar reverse((reverse $CODE) =~ m{
      \A
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) )*
      (>[^<>]*<)
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) | >[^<>]*< )*
      \z
    }x);
    print "backwards: $last\n";

    $last = scalar reverse($rCODE =~ m{
      \A
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) )*
      (>[^<>]*<)
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) | >[^<>]*< )*
      \z
    }x);
    print "backcache: $last\n";


timethese(-15, {
  'forwards' => << 'END',
    ($last) = $CODE =~ m{
      \A
      (?: <[^<>]*> | " [^"\\]* (?: \\. [^"\\]* )* " | (?>[^"<>]*) )*
      (<[^<>]*>)
      (?: " [^"\\]* (?: \\. [^"\\]* )* " | (?>[^"<>]*) )*
      \z
    }x;
END
  'backwards' => << 'END',
    $last = scalar reverse((reverse $CODE) =~ m{
      \A
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) )*
      (>[^<>]*<)
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) | >[^<>]*< )*
      \z
    }x);
END
  'back+cache' => << 'END',
    $last = scalar reverse($rCODE =~ m{
      \A
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) )*
      (>[^<>]*<)
      (?: " (?: [^"\\]* .\\ )* [^"\\]* " | (?>[^"<>]*) | >[^<>]*< )*
      \z
    }x);
END
});