I'm having a hard time getting a "grasp" on your problem, I'm in "fuzzy" mode this morning. But this is what pops into my head, and maybe it will help you.

The search method allows for a "kind" of search, either 'exact' or 'regexp', and maybe you can use that to your advantage. Have you looked at the widget demo, for " A search tool built with a text widget" ? It has a great sub:

sub search_text {

    # The utility procedure below searches for all instances of a give
+n
    # string in a text widget and applies a given tag to each instance
+ found.
    # Arguments:
    #
    # w -    The window in which to search.  Must be a text widget.
    # string -    Reference to the string to search for.  The search i
+s done
    #           using exact matching only;  no special characters.
    # tag -    Tag to apply to each instance of a matching string.
    # kind    rexexp or exact

    my($w, $string, $tag, $kind) = @_;

    return unless ref($string) && length($$string);

    $w->tagRemove($tag, qw/0.0 end/);
    my($current, $length) = ('1.0', 0);

    while (1) {
    $current = $w->search(-count => \$length, "-$kind", $$string, $cur
+rent, 'end');
    last if not $current;
    warn "Posn=$current count=$length\n",
    $w->tagAdd($tag, $current, "$current + $length char");
    $current = $w->index("$current + $length char");
    }

} # end search_text
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Maybe you could compare the search results between exact and regexp, and filter according to your needs?