map {$_ eq 'Oracle'? ($x):($x=$_)[2]} reverse @arr
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Next we process each element of the reversed array. If 'Oracle' is found, we return "$x". You way well ask - what is $x, and where did it get a value?

That happens if $_ does NOT match. In that case, what happens is:
* $x gets assigned the current element
* a temporary LIST is generated because of the () - this contains ($x)
* We index index into the second element ($x)[2] which does not exist
*resulting in an EMPTY list
*That gets sent to "map" which ignores that.

SO - the only elements that "map" returns is the $x value when the current element is 'Oracle'. In this case, $x contains the value of the previous element, and because we are 'reversed', in real life, it contains the 'next' element.

There is a potential complaint that the order of the returned values is reversed.
This is easily fixed by throwing a 'reverse' in front of the 'map'.