Benchmark block

[Jonathan via Digitalmars-d]

I have no idea if this has been discussed yet, but I was thinking 
it would be neat to have benchmark blocks that only run when 
specified, like how unittest works.

Code:

benchmarks
{
  import std.conv : to;
  int a;
  void f() {auto b = to!string(a);}
  auto r = benchmark!(f)(10_000);
  auto f0Result = to!Duration(r[0]);
  writeln(f0Result)
}

Example:
rdmd -benchmarks -main myapp.d

Alternatively, the writeln could be replaced with some kind of 
standard benchmark output utility (similar to the idea of assert 
when used for unit tests).

Thoughts?