A text string must be enclosed by matching pair of quotes (" or ').
Quotes are allowed in a string when they are of a different type from the enclosing quotes, i.e. "Can't" or '"sometimes"' (interpreted as Cant and sometimes).
If a semicolon (;) appears in a text string, it is interpreted as terminating the text string and a warning is given. This guards against the consequences of failing to terminate the test string with a quote.