my $t = 1;
grep { $t^=1 } LIST

[download]

If you're on perl-5.10 or newer, you can also use a state variable inside the block, and thus not "tainting" the outer scope: 

use 5.010;

say grep { state $t = 1; $t ^= 1} <a b c d>;

# prints: bd

[download]

In reply to Re: Mini-Tutorial: Working with Odd/Even Elements by moritz
in thread Mini-Tutorial: Working with Odd/Even Elements by ikegami

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