How do I pass values entered in the textfield into a hash?

ltran has asked for the wisdom of the Perl Monks concerning the following question:

How would I pass the values entered in the textfield into a hash as parameters i.e. people would enter something like this in the textfield;

1=>4, 3=>8
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and I would like to pass these as key-value pairs into a hash. How would I do it?

Originally posted as a Categorized Question.