Brushing up on Perl?

[Steve]

Ok I'm totally lost on this lovely little one liner.

MINE: {last MINE if ($x and grep defined,reverse
@{$x}{@{$c_data>{value} ||= []}})}

As I read it, it's basically saying

if $x and the result of grep is defined then reverse array at $x
With that array being comprised of either $_data at value or an empty value.
otherwise exit the loop

Thats not making much sense to me, can someone please help me figure
out what I'm missing here?