Once you have a working script, i think you still need to configure your apache server to run perl script as it's not set up by default. See
how do i configure apache webserver to run perl scripts, or hit google for more ...
Your code won't work:
- missing closing }
- your HTML is sending "Add" as value to the script, and you are testing on "addition" which will never match. I think you can just send the operators in the values, eg. +, -, *, /, **, and just use it for calculation. Then you don't have to test on $oper. You do need to test if it is one of the expected operator
Also your HTML is incorrect, missing closing </form> tag