when you send the /PROP command, you're telling the server you want the PROPERTIES assigned to whatever you specify (channel or nickname)...
on MSN, the PUID is the profile id property assigned to users. it has nothing to do with the MSNProfile property they specify when they connect (so you can catch scripters if their 'profile type' doesnt match what they actually have on their profile). to retrieve the PUID property, you specify that's what you want by sending this command to the server: /PROP <nickname> PUID
the response to that command comes in the form of raws 818-819:
818 - the response itself (containing the information you need)
* there will be more than one 818 call if you specify the wildcard (*) instead of a specific property. specifying the wildcard will give you ALL the properties you're allowed to see
819 - lets you know the response is finished