DISCLAIMER: I never used that module!

But it's obvious that your use of exists on scalar values is weird.

from this documentation of Net::Telnet ...

> When mode is "return" then the method generating the error places an error message in the object and returns an undefined value in a scalar context and an empty list in list context. The error message may be obtained using errmsg().

... I suppose you want to used defined instead.

FWIW: Another way is to keep the error-mode "die" and to catch the exception with a surrounding block eval (that's a try-catch in newest Perl).

Like that you'd get better diagnostics what went wrong.

Hope this helps! :)