Syntax error: "(" unexpected

[OckhamOdyssey]

Every time I try to run the example the following problem always appears:

./menu.sh: 16: ./menu.sh: Syntax error: "(" unexpected

I have noticed that this appears because the terminal tries to execute the script with sh, which doesn't allow some expressions, and not with bash. To solve it I think the best thing would be to change the first line of menu.sh to #!/bin/bash