Translation of strings/literals to varbinary?

I'm wondering if there is any documentation on the expected behavior
when a prepared statement is passed a representation of a varbinary?
I'm asking because when using perl's DBD::Sybase linked to the sybase
ctlib, I can set up the following prepared statement:

    my $sth = $dbh->prepare("SELECT foo_varbinary from db..mapped_value_map WHERE thing_id = ?");
    
I can then do the following, all of which return identical rows:
    my $vbinary = "00038600be24829d";
    $sth->execute(pack('H*', $vbinary);
or
    $sth->exeute($vbinary);
or
    $sth->execute("0x" . $vbinary);

However, when using DBD::ODBC via FreeTDS, only the first
representation of the varbinary works.  Is this something that
*should* work?  Or is the failure of the 2nd and 3rd forms an
oversight?  Is there any documentation on what values/representations
should be posible for doing this?

Thanks,

-Peter