my %hash;
push @{$hash{$_}}, $_ for @elements;
foreach (keys %hash) {
    # gets passed an array reference, deref if you so desire
    do_something_with($hash{$_}) if scalar @{$hash{$_}} > 0;
}

##</code><code>##

my @data;
foreach (keys %hash) {
    push @data, do_something_with($hash{$_})
        if scalar @{$hash{$_}} > 0;
}

##</code><code>##

my @elems = qw(foo bar baz quux ichi ni san shi go roku hachi);
my $set = 3;
while(scalar @elems)  {
    do_something_with(splice(@elems, 0, $set));
}