Concatenating a plural

Hi, I’m importing email using an IMAP network call. I want to access the sender email, but $ .'from' is plural. I’ve tried to join and\or concatenate this, but that doesn’t work. How can I concatenate a plural? I would like to have it in the form: Sender1, Sender2, but I can’t figure out the correct way to use concatenate for this.
Connector V33.5

To concatenate a plural value, you need to use join.
join takes two arguments, the first is the separator and can be omitted, the second is a promise-chain run for each entry in the plural value.
The result of the promise-chain must be a text.

Network messages use a collection of text to store the receivers/senders, which has a type of plural entity text. You will have to tell join whether you want the key or the value of each entry.

$ .'from' => join ( ", " ) ( .key )


$ .'from' => join ( ", " ) ( .value )