Writing to stdin of a process

[Craig Dillabaugh via Digitalmars-d-learn]

I want to be able to write to the stdin stream of an external 
process using std.process.  I have the following small test app.

myecho.d
------------------------------------------------------------------

import std.stdio;

void main(string[] args)
{
   foreach (line; stdin.byLine()) {
         stdout.writeln(line);
   }
}

------------------------------------------------------------------

If I call this from the command line, it echo's back whatever I 
write
to it.

Then I have the following program.

testpipes.d
-------------------------------------------------------------------
import std.process;
import std.stdio;

void main( string[] args ) {

     auto pipes = pipeProcess("./myecho", Redirect.stdin );
     scope(exit) wait(pipes.pid);

     pipes.stdin().writeln("Hello world");
}
--------------------------------------------------------------------

If I compile and run testpipes.d, nothing happens.  I was 
expecting
it to echo back "Hello world" to me.

Can anyone tell me what I am dong wrong.