Remove duplicated string stored in variable

Question

I have a variable $var with this content:

var=word1,word2,word3,word1,word3

and I need to delete duplicate words and the results is required stored in the same variable $var.

Answer 1

Try

    var="word1,word2,word3,word1,word3"
    list=$(echo $var | tr "," "\n")
    var=($(printf "%s\n" "${list[@]}" | sort | uniq -c | sort -rnk1 | awk '{ print $2 }'))
 echo  "${var[@]}"

Answer 2

If open to perl then:

$ var="word1,word2,word3,word1,word3"
$ var=$(perl -F, -lane'{$h{$_}++ or push @a, $_ for @F; print join ",", @a}' <<< "$var")
$ echo "$var"
word1,word2,word3