この3つの正規表現を1つで実現できますか?
<rx2>((?:^|<br>)[  ]*)((?:h?t?p?p?s?:?/?/)?)([a-z][a-z0-9A-Z-]*\.)([!--0-9=?-Z_a-z~.]+/)([!-;=?-Z_a-z~]+)【TAB】$1https://$3$4$5【TAB】msg
<rx2>((?:^|<br>)[  ]*)(https:/)([a-z][a-z0-9A-Z-]*\.)([!--0-9=?-Z_a-z~.]+/)([!-;=?-Z_a-z~]+)【TAB】$1https://$3$4$5【TAB】msg
<rx2>((?:^|<br>)[  ]*)(ttps://)([a-z][a-z0-9A-Z-]*\.)([!--0-9=?-Z_a-z~.]+/)([!-;=?-Z_a-z~]+)【TAB】$1https://$3$4$5【TAB】msg