antti@antti-HP-Compaq-dc7100-SFF-PE271ET:~/Prolog$ swipl
Welcome to SWI-Prolog (Multi-threaded, 32 bits, Version 7.2.3)
Copyright (c) 1990-2015 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

For help, use ?- help(Topic). or ?- apropos(Word).

?- ['DCG1.pro'].
true.

?- go.
|: Antti debugs the Acer.

PARSE SUCCESSFUL
true 
?- go.
|: Antti yesterday debugged the Acer.

PARSE SUCCESSFUL
true 
?- go.
|: Antti debugs the Froob.

false.

?- go.
|: The man sings.

PARSE SUCCESSFUL
true 
?- go.
|: The man eats the apple.

PARSE SUCCESSFUL
true 
?- go.
|: The man eats the computer.

false.

?- halt.
antti@antti-HP-Compaq-dc7100-SFF-PE271ET:~/Prolog$