From Rosetta Code
Jacl is an implementation of Tcl. Other implementations of Tcl.

Jacl is an implementation of Tcl written in Java rather than the (more common) C version shared by tclsh and wish. The current version does not implement quite the same version of the language, does not include any support for Tk, and instead includes a package for closer Java integration (allowing the use of the AWT, Swing, SWT, etc. for GUIs if desired).

Consider using JTcl instead, which supports a larger fraction of the Tcl language and has more active developers working on it.