If debug mode is on ($_GET['debug']), then exit before redirecting.

Otherwise, the debug output will be lost upon redirect.
Apply subcommands before doing anything else.

Cameron Matthews reported that the following command was not working:

    split {url g porsche} {url y porsche} {url a porsche}

This was not working because we were applying subcommands (the stuff between {...})
only *after* converting the command to a URL. By that point, the {...} arguments were
already urlencoded to %7B...%7D and applying subcommands no longer recognized them
as subcommands.

The fix was to apply subcommands as the first step as well as later after the command
is converted to a URL.