what is "^-"?????

[aborruso at spaziogis.it]

Dear mapserver users,
I have seen in the template file of
"http://mapserver.gis.umn.edu/cgi-bin/mapserv?map
=%2Fms_demo%2Fdemo.map&layer=lakes&layer=streams&zoomsize=2" a string like
"^-". What does it mean?
It's exactly:

CLASS
    EXPRESSION "^-"
    COLOR 255 0 0
    OUTLINECOLOR 0 0 0
  END


Thank you,

Andrea