convert environment variables between scripting languages

 Output environment setting code for the target scripting language. Can
 report only differences or all environment variables.
 .
 For example, convert csh setup script to bash or the other way around.
 Or use it to simplify the creation of modulesfiles (cf. package
 environment-modules).
 .
 Support bash, csh, ksh, modulecmd, perl, plist, sh, tclsh, tcsh, vim,
 yaml, and zsh.