use_module/1 is of the wrong name for this functionality - it should be use_module_file/1 -- because it takes the name of a file, not the name of a module (unlike in Java, there is no convention regarding the mapping of a module name to a module file name -- nor a convention for a module hierarchy for that matter. Maybe that's something for ISO to look into.).
On the command line one should use
But you can also write
This will actually consult the file and reload the module. It's a bit quick and dirty.
Inside the program
If your program needs some extras but you are unsure whether they are around (because they haven't necessarily been compiled, for example):
From the module
prolog_pack.pl, to make sure an URL scheme is acceptable:
download_scheme(http). download_scheme(https) :- catch(use_module(library(http/http_ssl_plugin)), E, (print_message(warning, E), fail)).