Define a pattern for the map areas. PATTERN9 defines a single map pattern that is repeated for each of the 50 map areas (states). The pattern is an empty fill with a black border. VALUE= defines a map/plot pattern, which cannot be used by the blocks. Specifying a color causes PATTERN9 to generate only one pattern definition. REPEAT= specifies the number of times to repeat the pattern definition. 
pattern9 value=mempty color=black repeat=50;