First two points...
--My first publish, I will be adding to it. (EDIT: ITS been retired so maybe I wont. LOL.)

Third Point.
--I do not agree on the duplicate. In that Kata you are finding the DUPLICATED number.
In My kata you are finding the MISSING number, on top of that, you are finding the LOWEST MISSING number.

Will the code be similar? maybe. The theory here is called "Multiple Methods"
In helps to have problems worded differently so we work then in different ways.
And in this case the input is different.

This is my first publish. I am still a little confused on exactly what to do.
That was a mistake. Thanks for informing me.

Have you tried a regex?
/[a-zA-Z0-9.@]/gm

Also, besides letters, numbers, and the two characters you included (. and @).
Alot of other chars are allowed. i.e. (!#$%&'*+-/=?^_`{|}~ etc)