IIRC , the original patterns are pulled from a database, but in the above case pulling the patterns from a file each time could perhaps be avoided by reading them all in at once: 
open my $p, "< ". shift @ARGV
   or die "could not open pattern file: $!";
my @patterns = <$p>;
chomp @patterns;

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;
    }
}

[download]

Going back to the original pulling patterns from a db gives us: 

# 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;
    }
}

[download]

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In reply to Re^2: Searching pattern in 400 files and getting count out of each file by space_monk
in thread Searching pattern in 400 files and getting count out of each file by Rita_G

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