I dive out the problem might be that firefox 7 does not support anonymous functions.

No, firefox 7 supports and depends on anonymous functions

If I manually change the function () to function abc(), then repl can not get any references

:) yeah, don't do that

You're essentially changing return sub { print "call me" }; to sub named { print "call me" };

"sub {}" returns a function, but "sub name {}" returns nothing.

You're barking up the wrong tree :)