> [stdin:1] A system variable named `(ENOENT)' already exists
> Test unit `stdin': NOK (<stdin:1> syntax error)
+# Substitution usage
+! new=1
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+! unset new
+p new is empty <$new> and is len is <${#new}>
+# display 66 and assign 6 to the value 66 of the variable new
+p ${new:=66}
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+# display 66 and do not assign the value 69 to the variable
+p ${new:=69}
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+! unset new
+# display 79 and do not assigne the value 79 to the variable
+# new is empty
+p ${new:-79}
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+# display nothing and do not assigne the value 89 to the variable
+# new is empty
+p is empty ${new:+89}
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+! set new=999
+# display 99 and do not assigne the value 99 to the variable (do not dispaly the value of new)
+# new is empty
+p is empty ${new:+99}
+p new is `$new ' or `${new}'
+p the len of new is : ${#new}
+
+! unset new
+
+# p ${new:?new is empty}
