Also, PostgreSQL doesn't support placeholders for the number after the LIMIT.

Yes it does.

#!/usr/bin/perl -w
use strict;
use DBI;
my $dbh = DBI->connect("dbi:Pg:dbname=pfau")
    or die "Unable to connect to db: $DBI::errstr";
$dbh->{RaiseError} = 1;
my $s = $dbh->prepare("select relname from pg_class limit ? offset ?")
+;
my $r = $s->execute(3,10);
while (my @row = $s->fetchrow_array) {
    print "Table: $row[0]\n";
}
$s->finish;
$dbh->disconnect;
[download]

Produces:

Table: pg_attrdef
Table: pg_toast_17086_idx
Table: pg_trigger
[download]