how to modify only the last part of the variable
 

here is a variable
$name=000000000002312.cdt

after using it in a process
then it is required by the program to change the variable
$name=000000000002312.wlg

how can it be accomplished , in bash shell script.

Thank you

Another Note: the variable when assinged first is an user input.. after that, we need it to change only the extensions.. i dont know how to do it..

this substitutes the substring "cdt" that matches at the back end of the string.

Thank you . It is working.. am a newbie.. Appreciate ur prompt help..