my $html = do { local $/; <DATA> };

$html =~ s!(https*:\S*?)(\.*?\s)!<a href="$1">$1</a>$2!gm;

print $html;

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