Thank you'll very much for the pointers. It helped me trace through the problem. It's now resolved. I see build_tree was expecting a string that began with parenthesis, like so: "(TOP (S (NP (NP (NNP Pierre) (NNP Vinken))".

In reply to Re^4: Can't use an undefined value as a HASH reference by Anonymous Monk
in thread Can't use an undefined value as a HASH reference by Anonymous Monk

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