Extending DBI / DBD::ODBC for DB2/400

I'm using ODBC to access an IBM AS/400 DB2 backend. For my own use, I
inject a function (rexec) into the DBI::db namespace that allows the
following usage:

$dbh->rexec('dspfd file(*libl/mduser) type(*basatr)
output(*outfile) '
.'fileatr(*pf) outfile(qtemp/dspfdout)');

my $libs = $dbh->selectcol_arrayref("select atlib from
qtemp.dspfdout");

'dspf' is an OS command native to the backend. 'rexec' allows me to
execute arbitrary OS commands. Many OS/400 commands create database
tables via the *outfile directive, allowing me to query the resulting
tables.

Here's the rexec sub. I probably shouldn't be monkeying with DBI::db,
but, hey, perl gives you plenty of rope to hang yourself, right?

sub DBI::db::rexec {
my ($self, $cmd) = @_;

my $len = length $cmd;
# escape single quotes
$cmd =~ s/'/''/g;
$self->do(sprintf q{CALL QSYS.QCMDEXC('%s', %010d.00000)},
$cmd, $len);
}

This (and perhaps other features specific to DB2/400) might be useful
for others, and even for my own usage, I would like a cleaner way to
implement it so I can use it easily in my application code and with
DBIx::Class, etc.

So, what is the "proper" way to extend DBI or DBD::ODBC to make "rexec"
available as transparently as possible?

.