countup.pl

#!/usr/bin/env perl
use strict;
use warnings;
use utf8;
use IO::Handle;
use Time::HiRes qw(sleep);


for my $i (1 .. 100) {
    sleep 0.02;
    my $msg = "counting...$i/100";
    progress_print($msg);
}
for my $i (reverse 1 .. 100) {
    sleep 0.02;
    my $msg = "counting...1/$i";
    progress_print($msg);
}

print "\n\n";


{
    my $prev_msg_len;
    BEGIN { $prev_msg_len = 0 }

    sub progress_print {
        my $msg = shift;

        # delete previous message.
        print ' ' x $prev_msg_len;
        $prev_msg_len = length $msg;

        # print message.
        print "\r$msg";
        STDOUT->flush;
    }
}