bash script fail execute in org-babel block

Question

Below bash script works as a bash script but if execute it in org-babel block as below, it report error:

sh: 2: Bad substitution

code:

#+begin_src sh :results output
str="toto.titi.12.tata.2.abc.def"
arr=${str//[!0-9]/ }
echo "${arr[@]}"
#+end_src