I guess you need to unescape the URI in $new_location, i.e. 

use URI::Escape;

my $location = "http://www.google.com/sorry/?continue=http://www.googl
+e.com/search%3Fq%3Dperlmonks";

my $new_location = $location;
$new_location =~ s/.*\/sorry\/\?continue=(.*)/$1/;
$new_location = uri_unescape($new_location);

print "   $location\n=> $new_location\n";

__END__
   http://www.google.com/sorry/?continue=http://www.google.com/search%
+3Fq%3Dperlmonks
=> http://www.google.com/search?q=perlmonks

[download]

That said, I don't get any captchas or sorries from Google (is this still your squid's sorry thing?), so I couldn't test it as is... but when I submit an incorrect search, e.g. 

    http://www.google.com/search?=perlmonks

[download]

(i.e. missing q, as in your OP), Google redirects me to http://www.google.com/webhp, so I used that response to test, and when I rewrite the Location to 

    if ($location =~ m|/webhp$|) {
        my $new_location = "http://www.google.com/search?q=perlmonks";
        $headers->header( Location => $new_location );
    }

[download]

things work fine for me, while with the escaped http://www.google.com/search%3Fq%3Dperlmonks I do get a 404 Google custom error page.

In reply to Re^6: Unfinished custom proxy by Eliya
in thread Unfinished custom proxy by kazak

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.