And now for something completely different...

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1191833

use strict;
use warnings;

my @x=qw/d b c e a f/;
my @y=qw/4 6 5 2 9 1/;

my @answer;
@answer[@y] = @x;
@answer = (grep defined, reverse @answer)[0..3];

print "@answer\n";
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