my @sorted_recs = map { $_->[0] } 
    # This first map executes last, after the sort is done.
    # it strips away the datastructure container along with the
    # sort criteria information, leaving only the original
    # datastructure, in sorted order.
                  sort { $a->[1] <=> $b->[1] }
    # Sort executes after the second map is done.  Sort is being told
    # to sort on the floating point number being used as the
    # sort criteria.

                  map { [ $_, (split /:\s*/, $_->[3])[1] ] }
    # The final map executes first.  It creates a container
    # datastructure.  Each element contains an array ref to a two
    # element array.  The first element is your original record.
    # The second element contains only the floating point
    # number you're trying to sort on.
                  @records;