I'm trying to create two javascript bookmarklets:

1. Take the current URL of the page and open a new window with a URL
based on the current page. Some examples (I use "->" to mean "this
URL turns into that URL"): 

http://example.edu/som/faculty_staff.cfm#HeaderTitle -> https://authoring.example.edu/som/login.cfm
http://example.edu/som/faculty_staff.cfm -> https://authoring.example.edu/som/login.cfm
http://example.edu/som/ -> https://authoring.example.edu/som/login.cfm
http://example.edu/news/webpublishing/index.cfm -> https://authoring.example.edu/news/webpublishing/login.cfm

2. Take the current URL of the page and open a URL (in the same window) based on the current page.  Some examples:

http://example.edu/som/faculty_staff.cfm#HeaderTitle -> https://authoring.example.edu/som/faculty_staff.cfm
http://example.edu/som/faculty_staff.cfm -> https://authoring.example.edu/som/faculty_staff.cfm
http://example.edu/som/ -> https://authoring.example.edu/som/
http://example.edu/news/webpublishing/index.cfm -> https://authoring.example.edu/news/webpublishing/index.cfm

I plan to use these bookmarklets in sequence, first pressing 1 to log into the CMS, then pressing 2 to edit the current page.

I'm a regex newb. I thought this would be a simple enough problem that I could teach myself some regex and figure it out. But I'm having trouble even getting started. 

Many thanks in advance for any help!