There's discussion of this e.g. in Threading: Invalid value for shared scalar. The executive summary appears to be that you cannot share nested structures this way - structures such as an array containing not simple scalars, but references to more complex structures, e.g. Net::Telnet objects.

In that same (Perlmonks) thread djantzen also points to How to share huge data structure between threads? for sample code for how to share nested structures.