Nice, but why the bit ops? This isn't assembler. 
sub interleave { @_[ map $_ % 2 ? $_ / 2 : ( $_ / 2 ) + ( $#_ / 2 ), 1
+ .. @_ ] }

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Now there are several things that irk me. One is the duplication of $_ / 2. The other is 1 .. @_ which surprised me for 1/10th of a second. 
sub interleave { @_[ map $_ / 2 + ( $_ % 2 ? $#_ / 2 : 0 ), 0 .. $#_ ]
+ }

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Now IMHO it's much easier to see what's going on. But I'd write it differently: 
sub interleave { @_[ map +( $_, $_ + @_ / 2 ), 0 .. $#_ / 2 ] }

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That gets us rid of the constant evaluation of a condition and reduces the number of iterations by half. You might want to move the @_ / 2 invariant out of the loop as a final optimization. The inner loop is now extremly simple: two additions.

This is faster than your cryptic bit ops version and still clear as day to read. Don't microoptimize, pick a good algorithm first. You'll always get more readable as well as faster code.

Makeshifts last the longest.

In reply to Re: interleave (single shuffle) by Aristotle
in thread interleave (single shuffle) by ysth

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