According to this report, Tcl/Tk and Expect are used at the US DOD:

http://www.egovos.org/pdf/dodfoss.pdf

although they don't go into the specifics.

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Tcl 8.3 is blessed by DII COE [http://diicoe.disa.mil/coe/] as a COE Product. This effectively means that you can use this version of Tcl without special permission (and not affect your DII COE compliance). Perl is the only other scripting language listed (as of COE Version 4.6 Build List for Solaris/Windows/HPUX 09Jan03).