Without seeing the surrounding code it is difficult to say. However, this section from perldiag might point you in the right direction:

Variable ``%s'' will not stay shared
    (W closure) An inner (nested) named subroutine is referencing a le
+xical
    variable defined in an outer subroutine.

    When the inner subroutine is called, it will probably see the valu
+e of
    the outer subroutine's variable as it was before and during the *f
+irst*
    call to the outer subroutine; in this case, after the first call t
+o the
    outer subroutine is complete, the inner and outer subroutines will
+ no
    longer share a common value for the variable. In other words, the
    variable will no longer be shared.

    Furthermore, if the outer subroutine is anonymous and references a
    lexical variable outside itself, then the outer and inner subrouti
+nes
    will never share the given variable.

    This problem can usually be solved by making the inner subroutine
    anonymous, using the sub {} syntax. When inner anonymous subs that
    reference variables in outer subroutines are called or referenced,
+ they
    are automatically rebound to the current values of such variables.
[download]

--
John.