In a way, your code is doing exactly what you say you want it to: it is indeed matching every line in @netstat that matches [your] @matches list", but the way perl interprets that probably doesn't capture what you're thinking, What your code does is give you every line in the netstat output that matches *your entire @matches array*, interpreting that array as a string. The matching operator is a double-quote context (just like print "@matches"). And, as it says in perldata:

Arrays and slices are interpolated into double-quoted
strings by joining the elements with the delimiter 
specified in the $" variable($LIST_SEPARATOR if 
"use English;" is specified), space by default.
[download]

In other words, the line:

my @results = grep( /@matches/, @netstat );
[download]

comes out (given the rest of your code) as equivalent to my @results = grep(/invalid headers packets dropped/, @netstat); in other words it's trying to find that whole "phrase."

I think you also mixed up your foreach loop, which loops over @netstat, when I think what you wanted was to check each element in @matches; putting all that together, I think your loop should be:

foreach my $match (@matches) {
    my @results = grep /$match/, @results;
    print @results;
}
[download]

HTH

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