<pre><code>sub foo {[$#{$_[!$||$|]}*@{$_[!!$_^!$_]}?@{$_[!$..!!$.]}[$_[@--@+]%
@{$_[$==~/(?=)//!$`]}..$#{$_[$??!!$?:!$?]},($)?!$):!!$))..$_[$--$-]%@{
$_[$]/$]]}-(!!$++!$+)]:@{$_[!!$^^^!$^^]}]}
</code></pre>

<p>update: I thought the word "puzzle" would imply this, but: <em>I</em> know what it does - I wrote it.  If the puzzle doesn't interest you, please don't waste any time on it.</p>

It takes two arrayrefs and returns a new arrayref with the contents of the second array rearranged such that the second part comes before the first part, split at a point based on the memory location of the first array. When the second array is empty or contains one item, just returns a copy of the second array. Equivalent to the following:
```
```
sub foo {
    my ($list1, $list2) = @_;
    my @output;
    if (@$list2 > 0) {
        my $split = $list1 % @$list2;
        @output = @$list2[$split .. $#$list2, 0 .. ($split - 1)];
    } else {
        @output = @$list2;
    }
    return \@output;
}
```
```
```
$list1 % @$list2
```
essentially picks a random place to split the array, based on
```
$list
```
which evaluates to the memory address of $list when evaluated in a numeric context.
The original mostly uses a lot of tautologies involving punctuation variables to obfuscate. e.g.
```
!$| | $|
```
is always 1
```
@- - @+
```
is always 0
Updated to note that
```
perltidy
```
was very helpful deciphering here, but it choked on
```
!!$^^^!$^^
```
, which it reformats to
```
!!$^ ^ ^ !$^ ^
```
, which is invalid Perl; it should be
```
!!$^^ ^ !$^^
```
. This might be the cause of RWendi's compile error.