... so (inferring what module is from how the test works) the module-command below causes the first word of its promiser to be canonified (which gets us cat_prefix) and used as "namespace" in which the text output by the command gets used to set variables, where =.*=.* lines are seen.  I'm mildly surprised we don't have an attribute we can set on the commands promise, to over-ride the "canonify first word of command" default and directly specify the namespace name to use ...