21. The computer program product of claim 19 , wherein the host language is Ruby.
19. A computer program product for integrating multiple programming languages, the computer program product comprising a non-transitory computer-readable storage medium including computer program code that comprises: a source code file stored on the non-transitory computer-readable storage medium, the source code file including computer code written in a host language, and inset computer code written in a domain specific language, the domain specific language being different from the host language; and means, stored on the non-transitory computer-readable storage medium, for defining the inset computer code according to the domain specific language in terms of the host language by relating tokens that include strings of characters from the domain specific language to corresponding tokens that include strings of characters from the host language and relating at least one grammatical rule for operations on tokens from the domain specific language to at least one corresponding grammatical rule for operations on tokens from the host language.