my @deletable_ids = qw( 1 2 3 );
my $delete_at_a_time = 100;
while ( @deletable_ids ) {
    my @delete_now;
    if ( scalar @deletable_ids > $delete_at_a_time ) {
        @delete_now = splice @deletable_ids, 0, $delete_at_a_time;
    }
    else {
        @delete_now = @deletable_ids;
        @deletable_ids = ();
    }
    my $in_clause = join q{,}, @delete_now;
    $dbh->do( "DELETE FROM t WHERE blah IN ($in_clause)" );
}

##</code><code>##

    my $qmarks = join q{,}, map { '?' } @delete_now;
    $dbh->do( "DELETE FROM t WHERE blah IN ($qmarks)",
              undef, @delete_now );