Since you have my @Result inside the loop, each iteration of the use creates a new @Result variable, which holds at most one item at the end of each iteration, because you push at most one line to it in each iteration.

$Outcome is a reference to the last of the arrays you create.

I guess what you actually want is to move the my @Result outside of the loop.

Also there's no reason for initializing the new array with () - my gives you a perfectly fine empty array already.

See also: Coping with Scoping.

Thank you moritz, actually I have many text files which I want to work through. My idea was, to process each file per loop with the same array and then to save the outcome (per reference) in different files. I have just tried it with my @Result declaration at the beginning i.e. above the loop. It works now! But: how can I empty this array if I start processing the next file? Thank you!

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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Perl 6 - second systems done right

@Result = (); # should empty your array for you.

Here am I again. I put @Result = () in the outer loop (here not showed), direct after foreach my $file(@files), now it works too (i.e. the array empties).