TCL/TK has its own l10n mechanism, but I like the gettext way.

0. Set the env variables:
   TEXTDOMAIN, TEXTDOMAINDIR (by default is /usr/share/locale)

1. In JDS Linux, we have a high quality unicode font, and set it as the default widget font:
   option add *font -gnu-unifont-medium-r-normal--16-160-75-75-c-80-iso10646-1 widgetDefault

2. Then set the default system encoding:
   encoding system utf-8

3. Run the tcl/tk scripts in utf-8 locales.

References:
1. How to Use Tcl 8.1 Internationalization Features
2. Tcl/Tk 汉化解决方案
3. http://jserv.sayya.org/tcl-i18n/