while( my $line = <DATA> ) {
  print $line if $. % 5 == 0 || eof(\*DATA);
}



__DATA__
line one
line two
line three
line four
line five
line six
line seven
line eight
line nine
line ten
line eleven

##</code><code>##

line five
line ten
line eleven

##</code><code>##

my ($sum, $count) = (0,0);

while (<DATA>) {
  $sum += $_;
  $count++;
  if ($count == 5 || eof(\*DATA) ) {
        printf "Sum: %4d, count: %2d, mean: %5.1f\n", 
            $sum, $count, $sum/$count;
        $sum = 0;
        $count = 0;
    }
}

__DATA__
61
23
30
444
368
438
467
44
812
430
992
469