Indeed if you worry about performance you should probably not use a shell call of "grep", but use the internal perl grep command.

Why not just simply open each file one at a time?

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

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NB. This post was edited several times.

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

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