#! /usr/bin/env perl
use Modern::Perl '2015';
use List::Util qw/sum/;
###

my $string = '56 65 74 100 99 68 86 180 90';
my %sums;
foreach my $el (split(/\s+/, $string)) {
    my $sum = sum(split(//, $el));
    push @{$sums{$sum}}, $el;
}
foreach my $sum (sort {$a<=>$b} keys %sums) {
    print join(' ', sort {$a cmp $b} @{$sums{$sum}});
    print ' ';

}
print "\n";