Given, 

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

[download]

Micro-optimized: 

my @b;
$b[ $_ ] = $a[ $_ ] - $a[ $_+1 ] for 0 .. $#a-1;

[download]

Micro-optimized further: 

my @b = @a;
$b[ $_ ] -= $b[ $_+1 ] for 0 .. $#b-1;
pop @b;

[download]

Well, I suspect those are faster. I didn't actually test.

In reply to Re^2: Abusing Map (Corrected second code block) by ikegami
in thread Abusing Map by writch

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