With a few hours, I could probably make the regex recognize URLs in any format, but absolute URLs will have to do. Try the following:

use strict;
use warnings;

$_ = join '',<DATA>,' ';
s/(\w+:\/\/.*?)(\.?\s|\)|\])/<a href="$1">$1<\/a>$2/ig; chop;
print;

__DATA__
Students can activate their UMSIS userids on-line by filling out and s
+ubmitting the form at https://umsis.miami.edu/sign-up.
...which can be obtained via the web at http://www.miami.edu/it-forms/
+.
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