I don't know which value is the unitialized one (mostly because you haven't shown any code besides the subroutine to give context), but I can give you a good clue as to how to find out.

Simply print out the variables for the line where the error is occurring.  If it's the last one, try something like:

printf "TFD> count is '%s'\n", $count;
printf "TFD> path[count] is '%s'\n", $::path[$count];
printf "TFD> direntry[count] is '%s'\n", $::direntry[$count];
printf "TFD> FileLabel is '%s'\n", $::FileLabel;
printf "TFD> DirLabel is '%s'\n", $::DirLabel;
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For something like treeref which is more than a mere scalar value, you can use the module Data::Dumper, which is invaluable in these situations:

use Data::Dumper;

printf "TFD> treeref => '%s'\n", Dumper(\$treeref);
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That should tell you pretty quickly if you have an undefined value, and exactly which it is.

Update:  I should have mentioned that I use the string "TFD" to mean "Temporary - for debug".  It's an easy way to add debugging information that can later be searched for and removed.