# get column 0 from all result rows simultaneously....
my $results = $sth->fetchall_arrayref([0]);
# error check here?
# results are ref to array of hashes, so convert to array
# we could avoid this and use "results" directly
my @patterns = map { $_->[0] } @$results;

for my $filename (@ARGV) {
    open my $f, "< $filename" or die "could not open $filename: $!";
    my @lines = <$f>;
    for my $pattern (@patterns) {
        printf "%s has %d matches for pattern /%s/\n",
        $filename,
        scalar(grep /$pattern/, @lines),
        $pattern;
    }
}