how can I use variable within the FROM statement.

Greeting experts!! ^_^
I am working on a store procedure within the sybase DB.
The code that I wrote below is a store procedure.
I am trying to retrieve a database name from sysdatabase (system table) and retrieve sysusers and sysalternates information from each database within the system.
When I try to run the program. I get a error saying "Error: Incorrect syntax near '@dbname'.
 (State:37000, Native Code: 66)" I was told from buddy that if I want to retrieve informations within all the DB. I have to use perl to do so. If there are way to work this out without perl, it will be a great help.
Cordially
SOY

----------------------------------------------------------------------------------------------------
--Create procedure
create procedure sp_altlist as

--Declaring variable
declare @dbname sysname(30)

--Declaring cursor
declare cur cursor for
select name from master..sysdatabases

--Open cursor
open cur

--Fetch cursor info to variable
fetch cur into @dbname

--Loop
while (@@sqlstatus = 0) --if complete
begin
   SELECT @dbname, l.name, alt_name=u.name
   FROM @dbname..sysalternates a, @dbname..sysusers u, master..syslogins l
   WHERE a.altsuid=u.suid and a.suid=l.suid
   --Fetch cursor info to variable
   fetch cur into @dbname
end

--Close cursor
close cur
deallocate cursor cur

go
----------------------------------------------------------------------------------------------------