prevent certain inputs, like "user at gmail com"

hi,

i have a"comment" field in my app which is kinda public, but i still
want to have certain control over of what a user can enter and what
not: eg not allowed are
- email addresses
- fake string like: "user at gmail com"
- ...
- ...

is there anything out there or am i better of using writing my own "validations"

thx tom

You can try to write your own, but if there's a *reason* for users to
try to leave email addresses in comments, some of the creative ones
will figure out ways around your filter. If it's really a concern,
manual moderation may be the only way to handle the issue.

--Matt Jones