[det]debug(+Topic,
+Format, :Args)user_error, but only prints if Topic is
activated through
debug/1. Args
is a meta-argument to deal with goal for the @-command. Output is first
handed to the hook
prolog:debug_print_hook/3.
If this fails, Format+Args is translated to text
using the message-translation (see
print_message/2)
for the term debug(Format, Args) and then printed to every
matching destination (controlled by debug/1)
using print_message_lines/3.
The message is preceded by '% ' and terminated with a newline.