If all you are trying to do is get a count of the hash elements that have 'yes' values, then:

use strict;
use warnings;

my %include = (    A => 'yes',
        B => 'no',
        C => 'yes',
        D => 'yes',
        E => 'no');

my $yes_count = grep /^yes$/, values %include;
print "There are $yes_count elements with 'yes'\n";
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