Most mystical of monks, I seek your wisdom today regarding what is undoubtedly an imperfect understanding of Perl arrays. I have an array of integers, and I would like to pair every two integers. Perhaps I should simply use a for-loop, but I am curious as to why my first solution does not work. 
use strict;
use warnings;
my $s = "foo bar baz qux 3 3 1 3";
my @a = split /\s/, $s;
splice(@a, 0, 4);
while (@a) {
    print (shift @a), (shift @a), "\n";
}

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My understanding is that the while will execute so long as there are elements in @a, and that shift will return the left-most element of the array, move all elements down by one, and shorten the array by one. I expected to receive as output: 
33
13

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But instead received: 
31 # and no newline!

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Please direct this flummoxed novice to an explanation which said novice failed to find via either RTFM or STFW. I would be most grateful!

In reply to arrays: shifting in while loop by ivanthemad

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