/usr/lib/tcltk/tclodbc2.5/pkgIndex.tcl is in tclodbc 2.5.1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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package ifneeded tclodbc 2.5 \ [list load [file join $dir libtclodbc2.5.so]]