The C4/Biblio.pm subroutines PrepHostMarcField and prepare_host_field both do the same thing, so should be merged.
In addition: 1) prepare_host_field: if ( $field = $host->field('100') || $host->field('110') || $host->field('11') ) - the '11' should be '111' 2) prepare_host_field has a 240 -> 773b, which should be 250a -> 773b, as it is in PrepHostMarcField 3) There's a difference in how the 773a is set: prepare_host_field uses 100ab | 110ab | 11ab, but PrepHostMarcField uses 100a | 110a | 111a