To use dynamically generated menus (eg. generated by wmconfig)
with blackbox small hack was added:
If first character of menu file is '|' the menu will be taken
from pipe command instead of file.  The example will explain what I mean.

In ~/.blackboxrc

session.menuFile:	| wmconfig --output blackbox

See README.PLD in documentation of wmconfig to find out how to tune
output for blackbox.