Validate entry to white/black lists

[Max Kipness]

Hi,
 
I'm new to regex and am trying to put together some code that will
validate an email address or domain before entry into the black and
white lists. I have a system setup in which you forward a spam message
to blacklist at mydomain.com and the script parses the spam email address
and adds it to the blacklist. Well I'm still debugging the script, but
regardless, I'd like to setup a validation process before the email
address is actually written to the blacklist. Because if an invalid
entry gets written, email stops getting processed and errors are written
to the log. 

I've put together the following based on searches through deja, but it
does not account for subdomains. And really, I don't care about
validating the actual characters, like the script does, just validating
that the entry will not break MailScanner with spaces, etc.
 
This is the regex so far:
 
if ( $email =~ /^[a-zA-Z][\w\-\.\&]{3,}\@\w[\w-]*\.\w+$/ or $email =~
/^@\w[\w-]*\.\w+$/ or $email =~ /^\*@\w[\w-]*\.\w+$/) then email is
valid...
 
I'm looking to allow:
 
xxxx at xxx.xxx
xxxx at xxx.xxx.xx
xxxx at xxx.xxx.xx.xx (not sure how many subs are valid)
@xxx.xxx
@xxx.xxx.xx
@xxx.xxx.xx.xx
*@xxx.xxx
*@xxx.xxx.xx
*@xxx.xxx.xx.xx
 
Can anyone help, or is there a better approach I should take?
 
Thanks,
Max