You're checking the length of the result of an 'or' between two calls to the param() sub. There is no context in your post, but I don't think that's what you want. Look closely at how your parentheses match up:
in reply to Checking for empty CGI params; this isn't working
(param('tele') || param('mobile'))
Do you want, instead, to check that one (or both) of the params "mobile" and "tele" are at least one character long?
If so, try this:
If not, please ask again, but be clear in your question what it is that you're looking for, and exactly how the code you have so far is not doing what you want. (For more on this, have a look at How do I post a question effectively?) It is difficult to tell what you're trying to ask, here.
elsif( length(param('tele')) || length(param('mobile')) )
Welcome to the Monastery, andrew - I hope you find what you're looking for here.