use v5.14;
use warnings;

say "INPUT: ",my $str = join " ", 11 .. 19;


my @matches = $str =~ m/(\d+) (\d+)/g ;

while (my ($c,$r) = splice @matches,0,2) {
  say "$c - $r";
}

##</code><code>##

INPUT: 11 12 13 14 15 16 17 18 19
11 - 12
13 - 14
15 - 16
17 - 18

##</code><code>##

use v5.14;
use warnings;

say "INPUT: ",my $str = join " ", 1..9;

my $stop=5;
while ( my ($c,$r) = ($str =~ m/(\d+) (\d)/gc) ) {
  say "$c $r";
  die unless $stop--;
}

##</code><code>##

INPUT: 1 2 3 4 5 6 7 8 9
1 2