bpipe loses ability to use "using" after "load"

[supernifty]

The "using" functionality is permanently broken if load is invoked in a stage. The following prints out "value is $value" instead of "value is goodbye":

loadme = {
  exec """touch bpipetest"""
  load "bpipetest"
}

try_use = {
    println("value is ${value}")
}

run {
    try_use.using(value: "hello") +
    loadme +
    try_use.using(value: "goodbye")
}