My problem appears to be the result of where 'sub promise (&) { $_[0] }' is placed in the file. If it is placed after the definition of the upto subroutine which uses it, I get the error message as before. If it is placed BEFORE the definition of the upto subroutine, it works as the book says.

I didn't think the placement of subroutines mattered in a file. Perhaps the subroutine prototype on the definition of promise is turning it into an anonymous sub.

In reply to Re^2: lazy evaluation of sub arg by drbean
in thread lazy evaluation of sub arg by drbean

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