... or just use split:

#!/usr/bin/perl
use strict;
use warnings; 
use 5.018;

#1174610

my $data="-8-18 -9-10 -8 -7 -9-10 -9 -6 -5 -8 12 -7-10 -8 -8 -8 -8 -6
-3  2  2 -2 -8  1 -2 -5 -1 -4 -6  6 -4 -6 -5 -1  0 -8 -6 -6
 3 -6 -3 -6 -2 -5 -5 -5 -4  4 -3 -2 -2 -3 -5  1  3 -7 -4  3
 1 -6 -5 -6  4 -5 -6 -5 -6  3  1 -5 -3 -2 -5 -1  3 -4 -3  4
 2 -8 -6 -7 -8 -8 -8  7 -8 -9 -9 -7 -8 -6 -8 -4 -7 -9 -9 -8";

my @data = split(/ +/,$data);
my $i=1;

for my $item(@data) {
    if ( $item =~/\d+-\d+/ ) {
        $item =~ s/(-\d+)/ $1/g;
        if ($i == 38 ) {
           print "\n$item  ";
           $i = 1;
        }else{
           print "$item  ";
           $i = $i+3;
        }
    }else{
        if ($i == 38 ) {
           print "\n$item  ";
           $i = 1;
        }else{
           print "$item  ";
           $i = $i+3;
        }
    }
}

=head

C:\> 1174610.pl
 -8 -18   -9 -10  -8  -7   -9 -10  -9  -6  -5  -8  12   -7 -10  -8  -8
+  -8  -8  -6
-3  2  2  -2  -8  1  -2  -5  -1  -4  -6  6  -4  -6  -5  -1  0  -8  -6 
+ -6
  3  -6  -3  -6  -2  -5  -5  -5  -4  4  -3  -2  -2  -3  -5  1  3  -7  
+-4  3
  1  -6  -5  -6  4  -5  -6  -5  -6  3  1  -5  -3  -2  -5  -1  3  -4  -
+3  4
  2  -8  -6  -7  -8  -8  -8  7  -8  -9  -9  -7  -8  -6  -8  -4  -7  -9
+  -9  -8

=cut
[download]

But the preceding reply (Re: Help with pattern matching quantifiers from tybalt89) is preferable, both for use of  __DATA__ and for the consistency of spacing between values in the output.

But it intrigued me to write the extra code to hold line lengths to a relatively narrow page or screen.