[texhax] Issue about `~' character

[hymie!]

I use $\sim$


In our last episode, the evil Dr. Lacto had captured our hero,
  Rodolfo Medina <rodolfo.medina at gmail.com>, who said:
> Hi all.
>
>I need to use the `~' character within an internet address so I want TeX
>not touse it as it usually does, i.e. doing nothing but prevent breaking. 
>Putting`\string~' does not help because that character occurs within
>an\openout... \write... \closeout environment.	How could I do?