[Regular Expression] excluding alphanumerical chars

[teo]

Hallo,

I need to match a word in its "absolute" way, that is

with no alphanumerical chars
before and after it :
only blank spaces and interpuntuaction are accepted.

I tried with
[\W]myword[\W]

it works, but
it misses the cases where myword is at
the beginning of the line
and
at the ending of the line

Here is a screenshot (13kb) of the situation:
http://www.zshare.net/image/immagine-gif-7rk.html
Here is the same texting text :

Per andare per galli con la speranaza però di alcuno per
Non vorrei -per ma anche per- quindi abbiamo .Per, cuiper e salame per.
Per Non vorrei per