Trigger/copy issue

I have the following setup and data file that I want to load using copy
(8.0.0, macos).  The trigger function is to "clean" the input data (see
earlier posts on the subject).  However, it seems as if the trigger
function is not doing what I would have thought.  I want it to replace
'-' in the data in certain columns with NULLs.  Here is the SQL and a
few lines of sample data (sorry, may be broken up due to issues in the
email line splits).

Thanks for any insights.

Sean


CREATE TABLE g_refseq (
                      g_refseq_id serial primary key,
                      species integer not null,
                      gene_id integer not null,
                      status VARCHAR,
                      nuc_acc varchar,
                      nuc_gi  integer,
                      prot_acc varchar,
                      prot_gi  integer,
                      chrom_acc varchar,
                      chrom_gi  integer,
                      chrom_start integer,
                      chrom_end   integer,
                      strand      char                      );

create or replace function tgf_g_refseq_clean() returns trigger as $$
begin
NEW.prot_acc:=substring(NEW.prot_acc from '[A-Z][A-Z]_[0-9]*');
NEW.nuc_acc:=substring(NEW.nuc_acc from '[A-Z][A-Z]_[0-9]*');
NEW.chrom_acc:=substring(NEW.chrom_acc from '[A-Z][A-Z]_[0-9]*');
if (NEW.prot_gi='-') THEN
   NEW.prot_gi:= 'NULL';
END IF;
if (NEW.nuc_gi='-') THEN
        begin
   raise notice 'we are here';
   NEW.nuc_gi:= 'NULL';
   end;
END IF;
if (NEW.chrom_gi='-') THEN
   NEW.chrom_gi:= 'NULL';
END IF;
if (NEW.chrom_start='-') THEN
   NEW.chrom_start = 'NULL';
END IF;
if (NEW.chrom_end='-') THEN
   NEW.chrom_end = 'NULL';
END IF;
return NEW;
end;
$$ language plpgsql;

create trigger tg_g_refseq_clean before insert or update on g_refseq
for each row execute procedure tgf_g_refseq_clean();

DATA BELOW

9    1246500    Provisional    -    -    NP_047184.1    10954455    NC_001911.1    10954454    348
    1190    -
9    1246501    Provisional    -    -    NP_047186.1    10954457    NC_001911.1    10954454
2157    2912    +
9    1246502    Provisional    -    -    NP_047187.1    10954458    NC_001911.1    10954454
3040    4590    +
9    1246503    Provisional    -    -    NP_047188.1    10954459    NC_001911.1    10954454
4623    5714    +
9    1246504    Provisional    -    -    NP_047189.1    10954460    NC_001911.1    10954454
5717    7117    +
9    1246505    Provisional    -    -    NP_047190.1    10954461    NC_001911.1    10954454
7141    7767    +
9    1246509    Provisional    -    -    NP_858065.1    31982990    NC_004843.1    31982989    8
457    +
9    1246510    Provisional    -    -    NP_858066.1    31982991    NC_004843.1    31982989    607
    1449    +
139    1343044    NA    -    -    -    -    NC_004971.1    32455274    160    417    +
139    1343045    Provisional    -    -    NP_862625.1    32455275    NC_004971.1    32455274
414    650    +