The transliteration operator  tr or  y (see tr/SEARCHLIST/REPLACEMENTLIST/cds in perlop) does not support character classes, so the expression
    $t_count=($text=~ y/[tT]/t/);
will substitute any of the characters  ] [ T t in   $text with a  t character and return the total count of characters so transliterated to  $t_count.

>perl -wMstrict -le
"my $s = 'ab]cd[efthiTj';
 my $count = $s =~ tr/[Tt]/t/;
 print $s;
 print $count;
"
abtcdtefthitj
4
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Also, the characters  | . (vertical bar, period) have no special meaning in a regex character class, so in the regex
    @a = m/([\d|\.]+)\D+/g;
the class  [\d|\.] is "the class of any decimal digit, vertical bar or period character". (Although escaping  | or  . in a class will do no harm.)