TCC: Unknown command "False"

#1
The second and third commands below do the right thing, namely, start DEVENV with the specified solution. But the third one also produces an odd error message. It's the same after starting with /IIPS.
Code:
v:\> echo %@regquery["HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\10.0\ProjectMRUList\File1"]
P:\dumbdirsrc\Micro.sln

v:\> start P:\dumbdirsrc\Micro.sln

v:\> start %@regquery["HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\10.0\ProjectMRUList\File1"]
TCC: Unknown command "False"

v:\>