This problem is caused by an unfortunate auto-delegation implementation in Tk. Tk::BrowseEntry inherits from Tk::Frame and delegates some options to the internal Tk::LabEntry subwidget. Unfortunately Tk::Frame itself uses some of the -label* options itself and auto-creates a Label. So under some circumstances (as in yours) you get an unwanted Label widget.

It seems that the correct solution would be patching Tk::BrowseEntry to pass all -label* options to the Tk::LabEntry subwidget:

--- Tixish/BrowseEntry.pm       (revision 1396)
+++ Tixish/BrowseEntry.pm       (local)
@@ -26,7 +26,17 @@ sub ListboxWidget  { "Listbox"  }
 sub Populate {
     my ($w, $args) = @_;
 
+    my %labelArgs;
+    while(my($k,$v) = each %$args) {
+       $labelArgs{$k} = $v;
+       delete $args->{$k};
+    }
+
     $w->Tk::Frame::Populate($args);
+
+    while(my($k,$v) = each %labelArgs) {
+       $args->{$k} = $v;
+    }
 
     # entry widget and arrow button
     my $lpack = delete $args->{-labelPack};
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Another solution would be to not use any of the -label* options when constructing the BrowseEntry, but configure the subwidget directly (the Subwidget name is "entry").

Or just use the optiondb? $mw->optionAdd("*BrowseEntry.Entry.background", $bgcolor, "startupFile"); ...