It's not really a Perl question, it's more of an organizational one. Bottomline, if you can be sick with all three, then use checkboxes. If only one, then use radio.

In your database you would have a table for all the kinds of sickness, a table for the patient id, and a table with a column for the patient id and one for the type of sickness id. You would join the patient and tables to do a query on any one patient.

HTML:
<input type="checkbox" name="stomach" value="1" />
<input type="checkbox" name="head" value="2" />
<input type="checkbox" name="feet" value="3" />

SICKNESS TABLE:
+----+---------+
| id | name    |
+----+---------+
|  1 | stomach |
+----+---------+
|  2 | head    |
+----+---------+
|  3 | feet    |
+----+---------+

PATIENT TABLE:
+----+---------+
| id | name    |
+----+---------+
|  1 | Bill    |
+----+---------+
|  2 | Susan   |
+----+---------+
|  3 | Mary    |
+----+---------+

STATUS TABLE:
+------------+----------+
| patient id | sickness |
+------------+----------+
| 1          | 2        |
+------------+----------+
| 1          | 3        |
+------------+----------+
| 2          | 1        |
+------------+----------+
[download]

Insert a row into the "patient-sickness" table for each type of sickness the patient has checked.