Yuck, please don't use goto. Perl has next and last, which means you nearly never need the evil goto. Also, you could have saved a couple temporary variables in various places; f.ex $RAW = join "", <DATA>; would have let you get away without @INFO. (Even better would have been to write $RAW = do { local $/; <DATA> }; .) print ".."; exit; is nearly always better written as die "..";.

Update { I forgot to mention: you should really check out Mark-Jason Dominus' excellent Program Repair Shop and Red Flags article series on Perl.com }

That said, I would have used Net::Ping (as already suggested), and I'd also use one of the Getopt::* modules to make the script more flexible. Here's one possible rendition:

#!/usr/bin/perl -w
use strict;

use Net::Ping 2.13; # earlier versions do not return ping time

use Getopt::Std;
my %opt = (
    i => 1,
    m => 65536,
    p => "udp",
    r => 20,
    t => 1,
);
getopts("a:i:m:p:t:r:", \%opt) and $opt{a} or die << "USAGE";
usage: $0 -a addr [-i minsize] [-m maxsize] [-p proto] [-r retr] [-t t
+imeout]
       -a   destination address
       -i   initial ping size in bytes [default: 1]
       -m   max ping size in bytes     [default: 63536]
       -p   protocol: tcp, udp, icmp   [default: udp]
       -r   maximum nr. or retries     [default: 20]
       -t   timeout in seconds         [default: 1]
USAGE

my ($addr, $bytes, $maxsize, $proto, $timeout, $retries) =
    @opt{qw(a i m p t r)};

$Net::Ping::max_datasize = 65536; # we want to send huge packets

until($bytes > $maxsize) {
    my $p = Net::Ping->new($proto, $timeout, $bytes);
    $p->hires(1); # precise ping times

    my ($success, $time);
    my $retry = 0;

    ($success, $time) = $p->ping($addr)
        until $success or (++$retry > $retries);

    die "Sorry, host $addr not found or network problem.\n"
        if not defined $success;

    die "Host $addr seems to have died at $bytes bytes packet size.\n"
        if $success == 0;

    printf "%3.2f msec for $bytes bytes packet size", $time;
    print " (traffic hiccuped, $retry tries)" if $retry > 1;
    print "\n";

    ++$bytes;
};
[download]

Update: now tested. I also just noticed that the documentation of Net::Ping says you can only set the data size to 1024 bytes at most. There's a constant for that limit in the module however; I added a line to remove that limit.

Makeshifts last the longest.