s/quotemeta('[')/quotemeta('x')/g;

##</code><code>##

s/\Q$array1{$count}\E/$array2{$count}/g;

##</code><code>##

$from = join('', @array1);  # or set up $from and $to
$to   = join('', @array2);  # to begin with

tr/$from/$to/;              # e.g. "abc" =~ tr/ab/xy/ ==> "xyc"