Javascript magic is used on this page. You need to make POST request manually. Here is POST request (from Firefox's HTTPFox extension):

termYear    2014
term    10
course_number   
multiCourse 
course_title    
instructor  
subject AAS
course_start_eval   -
course_start_time   -
course_end_eval -
course_end_time -
course_status   -
course_level    -
course_units    -
virtual -
termCode    201410
runMe   1
clearMe 1
reorder 
gettingResults  0
search  Search
_cf_nodebug true
_cf
_nocache true
[download]

And here is the code:

$mech->post("https://registrar.ucdavis.edu/courses/search/course_searc
+h_results_mod8.cfm", 
    Content => {

        termYear => "2014",
        term => "10",
        ...
        subject => "AAS",
        ...
    },
);
[download]