my @all = ('a', 'b', 'c', '1', '2', '3');
my ($numbers, $letters) = grep2 {/\d/} @all;

print "numbers: @$numbers\n";  # prints "1 2 3"
print "letters: @$letters\n";  # prints "a b c"

##</code><code>##


sub grep2 (&@)
{
    my $code = shift;
    my $true = [];
    my $false = [];
    foreach (@_)
    {
        if (&{$code}())
        {
            push @$true, $_;
        }
        else
        {
            push @$false, $_;
        }
    }
    return ($true, $false);
}

my @all = ('a', 'b', 'c', '1', '2', '3');
my ($numbers, $letters) = grep2 {/\d/} @all;

print "numbers: @$numbers\n";  # prints "1 2 3"
print "letters: @$letters\n";  # prints "a b c"
print "all: @all\n";