use Net::Ping;

$host = shift;
$p = Net::Ping->new();
$p{"timeout"} = 0.05; # or whatever

print "$host is alive.\n" if $p->ping($host);

$p->close();
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# $p{"timeout"}   is wrong 
# $p->{"timeout"} is correct
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#!/usr/bin/perl
use Net::Ping;

my ( @ips, @up );
$" = "\n";

while(<>) {
  chomp;
  push @ips, $_ if /^(\d{1,3}\.){3}\d{1,3}$/;
}

print @ips;
my $p = Net::Ping->new( "syn", 5 );
$p->{port_num} = 7;

$p->ping($_) for (@ips);
while ( my ( $host, $rtt, $ip ) = $p->ack ) {
  push @up, $ip;
}

print @up;
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use strict;
use Win32::PingICMP;

my $p = Win32::PingICMP->new();

foreach (qw /www.yahoo.com www.cpan.org www.perlmonks.org/) {
    if ($p->ping($_)) {
        print "Pinging to $_ took ".$p->details->{roundtriptime}."\n";
    } else {
        print "Pinging $_ unsuccessful: ".$p->details->{status}."\n";
    }
}
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our @hosts = qw /www.yahoo.com www.cpan.org
                 www.perlmonks.org bob.net/;
our %host_state = ();

#our @alive = `fping -a @hosts`;
# 2>/dev/null keeps us from get error messages for fping
our @alive = `fping -a @hosts 2> /dev/null`;
chomp @alive;
for my $host (@alive) {
    $host_state{$host} = 1;
}
for my $host (@hosts) {
    print $host, " is ";
    print $host_state{$host} ? "alive" : "dead";
    print "\n";
}
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Minimal example code from an old script (assuming *NIX/Linux here):

#!/usr/bin/perl -l

use strict;
use warnings;

die "Usage: $0 <net>\n" unless @ARGV == 1;

# Rudimentary check on the argument
(my $net=shift) =~ s/\.0+$/./
  or die "Supply an IP of the form <#.#.#.0>\n";

print "Begun pings at " . localtime;

my @p;
open $p[$_], "-|", "ping $net$_ -c 10" or
  die "Couldn't start ping for $net$_: $!\n"
  for 1..255;

shift @p;
undef $/;
print map <$_>, @p;

__END__
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