Arrays are indexed from zero. So it's behaving as expected. If you want to delete "a," "c," and "e" they are elements 0, 2, and 4.

use strict;
use warnings;
use YAML;
my $array = [ "a" .. "e" ];
delete @{$array}[0,2,4];
print Dump $array;
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Hating splice is weird...