It works perfectly for me:

while ( $google_results =~
        m|<p class=g><a href=(http://.+?)\sonmousedown|gs) {
  push @links_found, $1;
}
print "$_\n" for @links_found;
__END__
http://www.ets.org/toefl/
http://www.ets.org/testcoll/
http://www.test.com/
[download]

BTW, it's a bit perverse to pick a character like |, which has a special meaning within regexps, as your delimiter for m.