If you use the new MathObjects (formerly called Parser objects), you can easily include custom answer checkers that could do more sophisticated checking of answers. You should look at the MultiPart object (in pg/macros/parserMultiPart.pl), and the custom answer checkers (in pg/macros/answerCustom.pl). There are some comments at the beginning of these files that should help. Also there are some examples in the past discussions. Try
http://65.206.22.46/moodle/mod/forum/discuss.php?d=1199
http://65.206.22.46/moodle/mod/forum/discuss.php?d=1180
http://65.206.22.46/moodle/mod/forum/discuss.php?d=1102
http://65.206.22.46/moodle/mod/forum/discuss.php?d=1089
http://65.206.22.46/moodle/mod/forum/discuss.php?d=1077
for starters.
Davide
WeBWorK Problems
manipulating webwork answers
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