Change my to our and it works.

Paraphrasing "perldoc -f my",
the variable is local to the enclosing block, file, or "eval".

From perldoc -f our

    our EXPR
    our TYPE EXPR
    our EXPR : ATTRS
    our TYPE EXPR : ATTRS
            "our" associates a simple name with a package variable in 
+the
            current package for use within the current scope. When "us
+e
            strict 'vars'" is in effect, "our" lets you use declared g
+lobal
            variables without qualifying them with package names, with
+in the
            lexical scope of the "our" declaration. In this way "our"
            differs from "use vars", which is package scoped.
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More discussion at this node.

Update:I would strongly recommend using poolpi's(++) method, below.