map might be an easier way to do this.

my $data = [1,0,1,2,3,4,5,6,7,8,9,11,2,2,3,34,5,6,7,8,81];

output($data);

sub output {
    open my $fh, '>>', "output.txt";
    print $fh map {"$_\n"} @{$_};
    close $fh;
}
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If you use qw, then you need to change the call to output.

my @data = qw( 1 0 1 2 3 4 5 6 7 8 9 11 2 2 3 34 5 6 7 8 81 );
output(\@data);
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