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

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

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));
}