BeanShell is an interpreter for Java similar to JACL or Jython that allows runtime experimitation with Java code.
BeanShell can be found at http://www.beanshell.org
The primary advantage of BeanShell for the Java programmer (presumably) is that it uses Java as the scripting language (BeanShell slightly loosens the syntax to allow things like dynamic typing). Thus one can use BeanShell to script Java components/classes without having to know another language (like Jython [L1 ], Tcl, Javascript, JRuby, Kawa scheme, etc)
The author of BeanShell is explicit that Tcl was the inspiration for BeanShell