'''DUP''' is a Forth-like esoteric programming language invented by Ian Osgood. DUP is a variant/enhancement of Wouter van Oortmerssen’s FALSE language.
Changes from FALSE include:
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Change of operators: DIV (integer division) changed to Forth-like MOD/DIV, new OVER operator etc.
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String output changed to string definition. Output has to be handled separately.
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Return stack is fully accessible and can be manipulated.
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Operator definition and override is possible. Access to full Unicode array of symbols for operator names.
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[http://www.quirkster.com/iano/js/dup.html| Osgood’s online Javascript DUP interpreter]