Run Time Substitution no Mapserver - Mapfile 2

gistfile1.rb

LAYER
    NAME 'municipios_selecao'
    STATUS DEFAULT
    TYPE POLYGON
    DATA 'municipios.shp'
    FILTER ([idmun]=%idmun%)
    VALIDATION
        'idmun' '^[0-9]{1,3}$'
    END
    CLASS
        NAME 'Seleção' 
            STYLE
                WIDTH 2
                OUTLINECOLOR 218 0 0
                COLOR 240 60 0
            END
    END
END