/usr/share/tcltk/itk3.3/pkgIndex.tcl is in itk3 3.3-4ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # Tcl package index file, version 1.0
package ifneeded Itk 3.3 [list load [file join /usr lib "libitk3.3.so.1"] Itk]
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