Language Details: Factor

Factor belongs to the family of concatenative languages: this means that, at the lowest level, a Factor program is a series of words (functions) that manipulate a stack of references to dynamically-typed values.

Official website (see also: Wikipedia article)
Code Jam 2011 Contestants using Factor
Qualification Round
Used in 5 solutions by 2 contestants:

Submission Origin

France (1 contestant)
Japan (1 contestant)