/usr/lib/tcltk/Trf2.1.4/pkgIndex.tcl is in tcl-trf 2.1.4-dfsg2-1.
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 Trf 2.1.4 \ [list load [file join $dir libTrf2.1.4.so]]