bash3.2.0 bug

gistfile1.txt

--------------------
bash 3.2.0
--------------------
~$ bash --version
GNU bash, version 3.2.0(1)-release (x86_64-unknown-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

~$ [[ "hoge" =~ ho.. ]] && echo "${BASH_REMATCH[0]}"
hoge

~$ [[ "hoge" =~ ho(..) ]] && echo "${BASH_REMATCH[0]}"
-bash: syntax error in conditional expression: unexpected token `('
-bash: syntax error near `ho(.'

~$ pattern="ho(..)"; [[ "hoge" =~ $pattern ]] && echo "${BASH_REMATCH[0]}"
hoge

~$ pattern="ho(..)"; [[ "hoge" =~ $pattern ]] && echo "${BASH_REMATCH[1]}"
ge


--------------------
3.2.57
--------------------

~ $ bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin16)
Copyright (C) 2007 Free Software Foundation, Inc.

~ $ [[ "hoge" =~ ho.. ]] && echo "${BASH_REMATCH[0]}"
hoge

~ $ [[ "hoge" =~ ho(..) ]] && echo "${BASH_REMATCH[0]}"
hoge

~ $ [[ "hoge" =~ ho(..) ]] && echo "${BASH_REMATCH[1]}"
ge

~ $  pattern="ho(..)"; [[ "hoge" =~ $pattern ]] && echo "${BASH_REMATCH[0]}"
hoge

~ $ pattern="ho(..)"; [[ "hoge" =~ $pattern ]] && echo "${BASH_REMATCH[1]}"
ge