A generalized approach to partitioning a list into sub-lists prior to processing the sub-lists (e.g., by writing each to an individual file):

c:\@Work\Perl\monks>perl -wMstrict -le
"use List::MoreUtils qw(part first_value);
 ;;
 use Data::Dump qw(dd);
 ;;
 my @data = (-10 .. 50, 60 .. 70, reverse 51 .. 59);
 dd \@data;
 ;;
 my @ranges = (1, 10, 18, 19, 41, 60);
 ;;
 my @parts = part { range_of($_, \@ranges) } @data;
 dd \@parts;
 ;;
 write_partition_to_file(@$_) for @parts[ 1 .. $#parts ];
 ;;
 sub range_of {
   my ($n, $ar_ranges) = @_;
   ;;
   my $r =
     first_value { $ar_ranges->[$_-1] <= $n && $n < $ar_ranges->[$_]; 
+}
     1 .. $#$ar_ranges
     ;
   return
     defined($r)            ? $r          :
     $n <  $ar_ranges->[0]  ? 0           :
     $n >= $ar_ranges->[-1] ? @$ar_ranges :
     die qq{range_of($n) failed}
     ;
   }
 ;;
 sub write_partition_to_file { print qq{@_}; }
"
[-10 .. 50, 60 .. 70, 59, 58, 57, 56, 55, 54, 53, 52, 51]

[
  [-10 .. 0],
  [1 .. 9],
  [10 .. 17],
  [18],
  [19 .. 40],
  [41 .. 50, 59, 58, 57, 56, 55, 54, 53, 52, 51],
  [60 .. 70],
]

1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17
18
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 59 58 57 56 55 54 53 52 51
60 61 62 63 64 65 66 67 68 69 70
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