fenom/docs/ru/mods/join.md

Modifier split

Join array elements with a string.

{$string|join:$delimiter = ","}

Returns an array of strings, each of which is a substring of $string formed by splitting it on boundaries formed by the string $delimiter.

{var $fruits1 = ["banana", "apple", "pear"]}
{$fruits1|join} output banana, apple, pear
{$fruits1|join:" is not "} output banana is not apple is not pear