Thanks for all your responses - using

$dbh->do("COPY node(taxid, name, tree_id, parent, children, rank, comm
+on_name) FROM STDIN");
$dbh->pg_putline("$_\tasdf\t4\t-1\treplace me\tqwer\tzxcv\n");
[download]

proves to be blisteringly fast. Cheers M