# we have @files
my $number_of_files = scalar(@files);
my $number_of_groups = 10;
my @groups;
for (1..$number_of_files) {
	my $modvalue = $number_of_groups % $_;
	push @{$groups[$modvalue]},$files[$_ - 1]);
}

##</code><code>##

{ my $counter = 0;
my $number_of_groups = 10;
for (@files) {
	push(@{$groups[$counter++]},$_);
	$counter = 0 if ($counter == $number_of_groups);
} }

##</code><code>##

my %groups;
push (@{$groups{substr($_,0,1)}},$_) for @files;

##</code><code>##

for (@files) {
	my $suffix = (m/\.(\w+)$/) ? $1 : 'none';
	push(@{$groups{$suffix}},$_);
}