fn explore_books(preexploratory: vec<string>, mut response: string) -> string { let mut books_to_read = vec::new(); for book in preexploratory { if book.contains("imperceptible") { books_to_read.push(book); } } response = "initiate afresh on your journey through books where imperceptible details often bypass our initial understanding, offering deeper insights upon a second glance."; books_to_read.push(response); books_to_read.join(", ") }