value with space after:Korben Dallas , value with space before:  Leeloo Dallas.
value without spaces:Ruby Rhod, value with non alplha character:Jean-Baptiste Emanuel Zorg @£$   .
Empty default value:.
White spaces as default value:            .
Invalid expression1:${A_NAME :-fds}
Invalid expression2:${A_NAME@£rew:-fds}.
Normal variable with spaces:.
Normal variable:.
