simple/multiping/multiping

#!/usr/bin/perl 
use warnings;
use strict;

use IO::Select;

my $s = IO::Select->new();

my %fh2host;
my $len = 0;
for my $host (@ARGV) {
    open(my $fh, '-|', 'ping', $host) or die "cannot exec ping: $!";
    $s->add($fh);
    $fh2host{$fh} = $host;
    $len = length($host) if length($host) > $len;
}
my %state;

for (;;) {
    my @ready = $s->can_read(1);
    for my $fh (@ready) {
	my $msg = <$fh>;
	chomp($msg);
	my $host = $fh2host{$fh};
	$state{$host} = $msg;
    }
    print "\n\n";
    for my $host (@ARGV) {
	no warnings 'uninitialized';
	printf("%-*s : %s\n", $len, $host, $state{$host});
    }
}