__DATA__
0039.04    N N OTH
0039.205.2 F T OTH
0039.205.6 F T TFF

should produce

0039NN       containing 0039.04    OTH
0039.205.2FT containing 0039.205.2 OTH
0039.205.6FT containing 0039.205.6 TFF
where the change in casetype changes the grouping

but instead the code produces

0039NN       containing 0039.04    OTH
0039.205.2FT containing 0039.205.2 OTH
0039FT       containing 0039.205.6 TFF