As currently implemented, if, in a moment of confusion, you pass in a variable directly instead of var=foo or msg=foo, the debug module’s output is less than helpful.
For instance, if I run this against a host:
It’s the way it’s not very good.
Basically “Hello World” is the default “msg”.
I would almost think that if there was no “=” in the line and the value was not a hash you could assume it was doing msg=“” maybe?