This proc is defined in tcl's package.tcl library file.

It is a routine called when a package require statement fails.
It is the default proc for the [package] unknown function. It's arguments
are the name of the desired package, version of the package, and -exact 
flag or nothing. It uses the [auto_path] variable to go looking through
the directories for a hit.

NB a recent (2006-2007) bug for users of [OpenCascade] on Windows (which uses Tcl to drive its test harness and other uses) is that if you have 8.4.14 installed and OpenCascade 6.1 then the command:

  package require BWidgets

replies:
  tclPkgUnknown name version ?exact?

This can be cured by renaming the directory C:\OpenCASCADE6.1.0\3rdparty\win32\tcltk to C:\OpenCASCADE6.1.0\3rdparty\win32\tcltkz (or any other name that is not in the path command).

Suggests that there are 2 versions of tclPkgUnknown in the sytem with different calling convetntions.

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[Category Package] [Category Command]