Ok I found the answer...
 
http://www.mail-archive.com/freeswitch-users@lists.freeswitch.org/msg12449.html
 
F
----- Original Message -----
From: Madovsky
To: freeswitch-users@lists.freeswitch.org
Sent: Monday, June 07, 2010 3:24 PM
Subject: vars scope in dialplan

example :
 
<extension name="blabla">
 <condition>
   <action application="set" data="test=cake"/>
 </condition>
 <condition field="${test}" expression="^(cake)$">
   <action application="set" data="prfx=00"/>
 </condition>
<condition field="${sip_to_uri}" expression="^(1\d{10,15})@$${domain}$">
 <action application="set" data="getPrfx=${prfx}"/>
</condition>
</extension>
 
but ${prfx} is empty.
I'm almost sure I didn't understand FS vars scope yet....
 
Thanks
 
Franck