And here is that threaded solution.

use strict;

use Config;
$Config{useithreads} or die "Recompile Perl with threads to run this p
+rogram.";

use threads;
use threads::shared;

use Time::HiRes qw ( time sleep);

our $starttime : shared;
our $linecount : shared = 0;
our $running : shared = 1;

sub progress {
    my $lasttime = $starttime;
    my $lastlinecount = 0;
    sleep(1);
    $| = 1;
    do {
        my $now = time();
        printf "\rline %d %8.1f avg lines per second %8.1f lines per s
+econd", $linecount, $linecount/($now - $starttime), ($linecount - $la
+stlinecount) / ($now - $lasttime);
        $lasttime = time();
        $lastlinecount = $linecount;
        sleep(.5);
    } while ($running);
};

$starttime = time();

our $thr1 = threads->new(\&progress);

while (1) {
    $linecount++;
    last if $linecount > 9999;
    sleep(0.001);
};
print "\n";
$running = 0;

$thr1->join();
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