You can run
the sample main from sbt:
$ cd scala
$ sbt
> run "(((lambda (x) (lambda (y) x)) 3) 4)"
Matthias Fleissen et al., Beyond Continuations, 1987. Technical Report, Indiana University http://www.ccs.neu.edu/racket/pubs/felleisen-beyond.pdf
Jonathan Tang, Write yourself a scheme in 48 hours, https://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours
Matt Might, Writing CEK-style interpreters (or semantics) in Haskell, http://matt.might.net/articles/cek-machines/