Bash pattern matching seems to be changed after bash-3.2-32.el5

Issue

• Bash pattern matching seems to be changed after bash-3.2-32.el5
• The scripts written for bash shell do not honour the regular expressions correctly in the recent bash versions.
• The below script works as expected in bash-3.2-32.el5

[root@localhost ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 5.8 (Tikanga)
[root@localhost ~]# rpm -qa | grep bash
bash-3.2-32.el5

[root@localhost ~]# ./regex.sh 
SUCCESS: SUDO updated
SUCCESS: SUDO updatedEEEEEEEEEEE
SUCCESS: SUDO updated
xxx
zzzzz
yyyyyyyyy

• However, the same script does not honour the regular expressions correctly in bash-4.1.2-15.el6_4.x86_64

[root@localhost ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 6.5 (Santiago)

[root@localhost ~]# rpm -qa | grep bash
bash-4.1.2-15.el6_4.x86_64

[root@localhost ~]# cat regex.sh 
#!/bin/bash

UpdateSUDOresult="SUCCESS: SUDO updated"
 echo ${UpdateSUDOresult}
 echo ${UpdateSUDOresult}EEEEEEEEEEE
echo ${UpdateSUDOresult} | grep "^SUCCESS: SUDO updated$"

 if [[ ${UpdateSUDOresult} =~ '^SUCCESS: SUDO updated$' ]] ; then echo xxx; fi
 if [[ ${UpdateSUDOresult} =~ 'SUCCESS: SUDO updated$' ]] ; then echo zzzzz; fi
 if [[ ${UpdateSUDOresult} =~ 'SUCCESS: SUDO updated' ]] ; then echo yyyyyyyyy; fi

[root@localhost ~]# ./regex.sh 
SUCCESS: SUDO updated
SUCCESS: SUDO updatedEEEEEEEEEEE
SUCCESS: SUDO updated
yyyyyyyyy