canguro,
Welcome to the monastery! I think you want a negated character class which is:

$message=s/<[^>]*>//g;

And the rest could be done like this untested code:

#!/usr/bin/perl
use warnings;
use strict;
use LWP::Simple;
my $site = "http://chart.yahoo.com/d?a=3&b=1&c=2003&d=3&e=11&f=2003&g=
+d&s=crio";
my $message = get("$site");
if ($message) {
    $message =~ s/<[^>]*>//g;
    print $message;
}
else {
    print "Error, get did not work\n";
}
[download]

But you really shouldn't be trying to parse HTML on your own unless this is truly just practice to sharpen your Perl skills.

Check out The CPAN for a myriad of modules concerning HTML and parsing. You are also going to want to use < CODE> < /CODE> tags around your code for formatting purposes.

Cheers - L~R