- (a) $hash{$col1} doesn't exist, or
 - $hash{$col1} exists, and...
  - (b) "$col2 _ $col3" gives an exact match to an existing key, or
  - (c) both $col2 and $col3 fall within the range of an existing key, or
  - (d) only $col2 or $col3 (not both) fall within the range of an existing key, or
  - (e) $col2 and $col3 define a range between existing keys, or
  - (f) $col2 and $col3 define a range that encompasses one or more existing keys,
        with extra margins at one or both edges.