The two above give good suggestions. Your problem at the moment, I think, is that you are only sharing that variable - any deep structure is not shared. See this from threads::shared:

           "share" will traverse up references exactly one level.
           "share(\$a)" is equivalent to "share($a)", while "share(\\$
+a)" is
           not.  This means that you must create nested shared data st
+ructures
           by first creating individual shared leaf notes, then adding
+ them to
           a shared hash or array.
[download]

I haven't tried it, but as BrowserUK points out the newer versions of threads::shared claim to do what you want.