/usr/lib/tkdnd2.6/pkgIndex.tcl is in tkdnd 2.6-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Tcl package index file
#
package ifneeded tkdnd 2.6 \
"source \{$dir/tkdnd.tcl\} ; \
tkdnd::initialise \{$dir\} libtkdnd2.6.so tkdnd"
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