You could do:

@b = map{ $a[ $_-1 ] + $a[ $_ ] } 1 .. $#a;

[download]

For small arrays, it doesn't cost too much.

Update: corrected bounds as pointed out by AnomalousMonk

But post-fix for is probably better:

$b[ $_-1 ] = $a[ $_-1 ] + $a[ $_ ] for 1 .. $#a;

[download]
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In reply to Re: Abusing Map (Corrected second code block) by BrowserUk
in thread Abusing Map by writch

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