Bareword "case" not allowed while "strict subs" in use at ./Shell.pl line
9.
Unquoted string "case" may clash with future reserved word at ./Shell.pl
line 9.
String found where operator expected at ./Shell.pl line 9, near "case 'y'"
        (Do you need to predeclare case?)
syntax error at ./Shell.pl line 9, near "case 'y'"
Execution of ./Shell.pl aborted due to compilation errors.