my $i      = $#{$before};

my %before = map { $before->[$_] => $_ } (0..$i);
my %after  = map { $after->[$_]  => $_ } (0..$i);

for (0..$i)
{
    print "$before->[$_] has moved from $before{$before->[$_]} to $after{$before->[$_]}\n"
        if $before{$before->[$_]} != $after{$before->[$_]};
}

#output:
#1 has moved from 0 to 4
#2 has moved from 1 to 0
#3 has moved from 2 to 1
#4 has moved from 3 to 2
#5 has moved from 4 to 3