I'm in a generous mood today, so here is a re-write of your script that should work a bit better than the original:

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

use HTML::TokeParser;
use LWP::UserAgent;

my %cities = (
        "City"
            => { var => 'adelmax' },
        "Elizabeth"
            => { var => 'elizmax' },
        "Noarlunga"
            => { var => 'noarmax' },
        "Mount Barker"
            => { var => 'mtbkmax' }
            );

my $ua = LWP::UserAgent->new();
$ua->timeout(60);
my $request = HTTP::Request->new('GET', 'http://www.bom.gov.au/cgi-bin
+/wrap_fwo.pl?IDS10034.txt');
my $result = $ua->request($request);
my $content = $result->content;

my $p = HTML::TokeParser->new(\$content);

my @lines;
while (my $tag = $p->get_tag("pre")) {
    my $text = $p->get_text("/pre");
    @lines = split /\n/, $text;
}

my $adeldesc;
my $cnt;

for my $line (@lines) {
    if ($line =~ /^Forecast for/ && !$adeldesc) {
        $adeldesc = $lines[$cnt+1];
    }

    if ($line =~ /^([\w\s]+):\s+Max\s(\d+)/) {
        $cities{$1}{max} = $2;
    }
    $cnt++;
}

my $out = "var adeldesc = $adeldesc\n";
for (keys %cities) {
    $out .= qq(var $cities{$_}{var} = "$cities{$_}{max}"\n);
}

open W, ">", "weather.js"
    or die "Could not open weather.js for writing:$!\n";
print W $out;
close W;

print <<EOF;
Content-Type: text/x-javascript
Pragma: no-cache
Cache-Control: no-cache
Expires: -1

$out
EOF
[download]

Output:

Content-Type: text/x-javascript
Pragma: no-cache
Cache-Control: no-cache
Expires: -1

var adeldesc = Fine and cool day with increasing high cloud.  Moderate
+ east to northeast winds.
var mtbkmax = "11"
var noarmax = "13"
var adelmax = "13"
var elizmax = "13"
[download]

As cwry pointed out, the reason it probably broke in the first place is because our good friends (and my ex-collegues) at the BOM decided to change "Adelaide City" to just "City". However, there were several other bad™ practices exhibited in your code, such as:

• not using warnings and strict,
• not checking the return value of your open,
• using multiple scalar variables, where a hash would be more appropriate
• and probably a couple more that I missed... ;)

Cheers,
Darren :)