Print is slow, you can try to speed up your solution by taking it out of the loop

print map {$i++ & 1 ? "" : "$_ "} reverse split(/ /);
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Also a common trick for a flip flop boolean state is inversion with xor $i^=1

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In hindsight you want grep not a map

$,=" ";
print grep { $i^=1 } reverse split(/ /);
[download]

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updated $,=" " , haukex++