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] [package unknown%|%unknown] function. Its 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.

<<discussion>>Obsolete bugs
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 conventions.

----
[MHo]: What's this?:
======
D:\Home\Arbeit1\pgm\tcl\usr\Tst\execx2\test>tclkitsh execx2test.tcl
invalid command name "tclPkgUnknown"
    while executing
"tclPkgUnknown execx2 0.1"
    ("package unknown" script)
    invoked from within
"package require execx2 0.1"
    invoked from within
"puts [package require execx2 0.1]"
    (file "execx2test.tcl" line 8)

D:\Home\Arbeit1\pgm\tcl\usr\Tst\execx2\test>tclkitsh
% info patch
8.4.19
%
======
This is ''not'' the case if I call tclsh 8.5.7 from ActiveState…
<<discussion>>
<<categories>> Package | Command