As brother anonymous has suggested, it looks like you have overwritten (c/w appending to) your system path environment variable with your own i.e.

SET PATH="C:path_to_my_perl"
[download]

instead of ...

SET PATH=%PATH%;"C:path_to_my_perl"
[download]

By doing so, you remove all the standard paths that Windoze uses to find its detritus - such as, for example, <c>cmd.exe>/c>...