What to you mean by "doesn't work"? It clearly works in the second snippet. If you want to report the number of single tests, process the output for /\d+\.\.\d+/. Something like this:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use List::Util qw{ sum };

my %test;
while (<>) {
    if (/^( *)([0-9]+)\.\.([0-9]+)$/) {
        my $length = length $1;
        my ($from, $to) = ($2, $3);
        $test{$length} += $to - $from + 1;
        --$test{$length - 4} if $length;
    }
}
say sum(values %test), ' tests run.';
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I only did minimal testing, so test it properly.