Typically you would do something like this:

for my $filename (@list_of_file_names) {
    process_file($filename);
}

sub process_file {
    my $filename = shift;

    open my $handle, '<', $filename
        or die "Can't open file '$filename' for reading: $!";
   my @Result;
   while(<$handle>) {
       next unless $_ =~/\d+\schunk/;
       s/\s+/ /g;
       push @Result, $_."\n";
   }
   # do something interesting with @Result here
}
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Thank you very much moritz, I did not dare write a subroutine yet. I have learned a lot today.