Any chunk of a container is also a container. That is, using chunk expressions, SenseTalk allows you not only to access specific lines, items, words or characters within text, but also to store into them, as long as the source value referenced by the chunk expression is itself a container.
Chunk expressions are described in detail in Chunk Expressions. Here are some examples showing access to a chunk as a container:
put "The movie was good" into rating
put "excellent" into the last word of rating
put rating --> "The movie was excellent"
put "last " before word 2 of rating
put rating --> "The last movie was excellent"