How to write replace string for object which will be substituted? [regexp]

[ryniek90]

Hi.
I started learning regexp, and some things goes well, but most of them 
still not.

I've got problem with some regexp. Better post code here:

"
 >>> import re
 >>> mail = '\nname at mail.com\nname1 [at] mail [dot] com\nname2 [$at$] 
mail [$dot$] com\n'
 >>> mail
'\nname at mail.com\nname1 [at] mail [dot] com\nname2 [$at$] mail [$dot$] 
com\n'
 >>> print mail

name at mail.com
name1 [at] mail [dot] com
name2 [$at$] mail [$dot$] com

 >>> maail = re.sub('^\n|$\n', '', mail)
 >>> print maail
name at mail.com
name1 [at] mail [dot] com
name2 [$at$] mail [$dot$] com
 >>> maail = re.sub(' ', '', maail)
 >>> print maail
name at mail.com
name1[at]mail[dot]com
name2[$at$]mail[$dot$]com
 >>> maail = re.sub('\[at\]|\[\$at\$\]', '@', maail)
 >>> print maail
name at mail.com
name1 at mail[dot]com
name2 at mail[$dot$]com
 >>> maail = re.sub('\[dot\]|\[\$dot\$\]', '.', maail)
 >>> print maail
name at mail.com
name1 at mail.com
name2 at mail.com
 >>> #How must i write the replace string to replace all this regexp's 
with just ONE command, in string 'mail' ?
 >>> maail = re.sub('^\n|$\n| |\[at\]|\[\$at\$\]|\[dot\]|\[\$dot\$\]', 
*?*, mail)
"

How must i write that replace pattern (look at question mark), to maek 
that substituion work? I didn't saw anything helpful while reading Re 
doc and HowTo (from Python Doc). I tried with 'MatchObject.group()' but 
something gone wrong - didn't wrote it right.
Is there more user friendly HowTo for Python Re, than this?

I'm new to programming an regexp, sorry for inconvenience.