#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1166921

use strict;
use warnings;

my @array = ("1","2","3","5","6","7","9");

my @ranges = "@array" =~
  s/\b(\d+)(?{$1})\K(?: (\d+)\b(??{++$^R!=$2}))+/:$2/gr =~ /\S+/g;

print "@ranges";