title: Concatenating lists in Raku
body: <p>I'm looking for a simpler solution.</p>
  
  <p>I have a list of prefixes with <em>corresponding</em> suffixes and a list of roots.</p>
  
  <pre class="lang-perl6 prettyprint-override"><code>my @prefixes = 'A'..'E';
  my @suffixes = 'a'..'e';
  my @roots = 1, 2;
  </code></pre>
  
  <p>I would like to make all the possible 'words': <code>A1a</code>, <code>B1b</code>...<code>A2a</code>...<code>E2e</code>. </p>
  
  <pre class="lang-perl6 prettyprint-override"><code>my @words;
  for @roots -&gt; $r {
      for @prefixes.kv -&gt; $i, $p {
          my $s = @suffixes[$i];
          my $word = [~] $p, $r, $s;
          @words.push: $word;
      }
  }
  say @words; # [A1a B1b C1c D1d E1e A2a B2b C2c D2d E2e]
  </code></pre>
  
  <p>I suppose that it is possible to do it much easier using something like <code>zip</code> or <code>cross</code>, but can't figure out how...</p>