Function expand_word 

pub fn expand_word(
    word: &Word,
    state: &InterpreterState,
) -> Result<Vec<String>, RustBashError>

Expand a word into a list of strings (with IFS splitting on unquoted parts).

Most expansions produce a single word. "$@" in double-quotes produces one word per positional parameter. Unquoted $VAR where VAR contains IFS characters may produce multiple words. Unquoted glob metacharacters are expanded against the filesystem.