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FETCHING THE VALUE OR VALUES OF A SINGLE NAMED PARAMETER:
...
Pass the param() method a single argument to fetch the value of the na
+med parameter. If the parameter is multivalued (e.g. from multiple se
+lections in a scrolling list), you can ask to receive an array. Other
+wise the method will return a single value.
If a value is not given in the query string, as in the queries ``name1
+=&name2='' or ``name1&name2'', it will be returned as an empty string
+. This feature is new in 2.63.