Why don't I get a LATIN1 encoding here with SET ENCODING?

I'm tracking another bug, but wanted to verify stuff on the command line.  I can't figure out why this did not work:

# psql dblack3-deleteme
Welcome to psql 8.3.8 (server 8.3.4), the PostgreSQL interactive terminal.
dblack3-deleteme=> create table bryce1 (key int,val1 text,val2 bytea);
dblack3-deleteme=> \encoding
UTF8
dblack3-deleteme=> SET CLIENT_ENCODING TO 'LATIN1';
SET
dblack3-deleteme=> \encoding
LATIN1
dblack3-deleteme=> insert into bryce1 values(1,2,'test\177');
INSERT 0 1

dblack3-deleteme=> insert into bryce1 values(1,2,'test\375');
ERROR:  invalid byte sequence for encoding "UTF8": 0xfd
HINT:  This error can also happen if the byte sequence does not match the encoding expected by the server, which is controlled by "client_encoding".

dblack3-deleteme=> insert into bryce1 values(1,2,'test\200');
ERROR:  invalid byte sequence for encoding "UTF8": 0x80
HINT:  This error can also happen if the byte sequence does not match the encoding expected by the server, which is controlled by "client_encoding".


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The underlying problem is a version upgrade of DBI drivers has broken some binary objects we used.
For the binary data:

<12><1>5<0><0><0><4>FOO1

<10><205><0><0><0><4>FOO2

Going in like so:

$sth->bind_param($index++, $data, {pg_type => $SQLDb::PG_BYTEA});

It now comes out munged:

\012 \001 5 \000 \000 \000 \004 FOO1

\010 \377 \000 \000 \000 \004 FOO