You perform a test to see if you matched the line with PING, but then perform the print on every cycle. Is this script more like what you want?

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

my $count    = 1;
my $interval = 5;
my $pkt_size = 128;
my $timeout  = 5;
my $phost    = 'www.google.com';

open CMD, "ping -c $count -i $interval -s $pkt_size -w $timeout $phost
+ |" 
  or die "Can't open ping: $!";

while (<CMD>) {
    # look for the line like: PING www.google.com (10.160.83.59): 56 d
+ata bytes
    next unless /PING\s+(\S+)\s+\(([\d.]+)\)/;
    print "host: $1\n";
    print "IP:   $2\n";
}
[download]

If you want to keep the values outside the loop: define the variable before the loop, then put the host/ip into the variables when you find them. Print at your leisure.

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

my $count    = 1;
my $interval = 5;
my $pkt_size = 128;
my $timeout  = 5;
my $phost    = 'www.google.com';

open CMD, "ping -c $count -i $interval -s $pkt_size -w $timeout $phost
+ |" 
  or die "Can't open ping: $!";

my $host;
my $ip;
while (<CMD>) {
    # look for the line like: PING www.google.com (10.160.83.59): 56 d
+ata bytes
    next unless /PING\s+(\S+)\s+\(([\d.]+)\)/;
    $host = $1;
    $ip   = $2;
}
print "host: $host has IP: $ip\n";
[download]

Cheers,
R.