Now that I have had time to look at this:

{@arr[$_,$_+1]} 0..$#arr-1
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Pardon me restating the obvious here.

There is no new functionality that I was unaware of. In this case $_ is an integer and you are just incrementing it. I was somehow originally thinking you where feeding the block a list of cities. This is still good stuff and I appreciate it.

I had started reading about the routines available in List::Utils and had dealing with the list values in my head. Looping over the indices may make more seance in this case.