Following is a demo of the task2.pl program.
?- talktome.
Right now...
the large yellow block is on the table
the large red block is on the table
the large blue block is on the table
the large green block is on the table
the small yellow block is on the table
the small red block is on the table
the small blue block is on the table
the small green block is on the table
Waiting for next inputs...
|: stack the small red block on the small blue block
Right now...
the large yellow block is on the table
the large red block is on the table
the large blue block is on the table
the large green block is on the table
the small yellow block is on the table
the small red block is on the small blue block
the small blue block is on the table
the small green block is on the table
Waiting for next inputs...
|: stack the large red block on the large green block
Right now...
the large yellow block is on the table
the large red block is on the large green block
the large blue block is on the table
the large green block is on the table
the small yellow block is on the table
the small red block is on the small blue block
the small blue block is on the table
the small green block is on the table
Waiting for next inputs...
|: pickup the red block
Error, failed to resolve reference.
Waiting for next inputs...
|: pickup the red block from the blue block
Right now...
the large yellow block is on the table
the large red block is on the large green block
the large blue block is on the table
the large green block is on the table
the small yellow block is on the table
the small red block is in the hand
the small blue block is on the table
the small green block is on the table
Waiting for next inputs...
|: