I have a value like "A1~B2~C3" in a multiple PV. Now I want to convert

3. Why do you need it to be multiple if the purpose is to make arrays out of a non-array

Appian 6.6.0

yes, it does

Actually we are getting the values from report & making them single using Join Array in Report when It has same Account and same SSN but they can have same SSN with two Accts so they can have values like A~B~C;D~E, that is why we are having it multiple.

Ah that's why, you are using an older version. The split function is designed to work with single valued text inputs, in newer versions that is not a problem but in yours you won't be able to use multi-valued strings with the split() functions which kind of makes sense since the purpose is to convert a text into an array therefore passing an array of text doesn't match the arguments of the function (although is handled correctly in newer versions)

Since you are in an old version of Appian you should try using the DoForEach plug-in. It has been deprecated but most likely you already have it in your environment, that way you can call this rule for each item in the array; you will pass the array to the doForEach while the rule that runs the split will be receiving a single item (the string to be converted to an array).

Another option that worked for me in 6.6.0 is:

=split(joinarray(substitute(ri!text,",","~"),"~"),"~")

Although you should consider upgrading, the support for 6.6.0 expired on 31 Jan 2013