Libtask is best explained by the docstring for TapedTask:
Libtask.TapedTask
The functions discussed the above docstring (in addition to TapedTask itself) form the
public interface of Libtask.jl.
They divide neatly into two kinds of functions: those which are used to manipulate
TapedTasks, and those which are intended to be used inside a
TapedTask.
First, manipulation of TapedTasks:
Libtask.consume
Base.copy(::Libtask.TapedTask)
Libtask.set_taped_globals!
Functions for use inside a TapedTasks are:
Libtask.produce
Libtask.get_taped_globals