Although this answer doesn't exactly match your question, I'm suspecting you did not take into account urls that start with something like homely
that will match the rules
Update: Like @Smirnov says below a the pattern could be simplified to ^((home|admin)(/|$))
Hence this Regex should work: ^(((home|admin)/)|((home|admin)$))
It will match paths that are exactly home or admin and have no trailing slash or paths that start with home or admin and have trailing slashes.
You can easily test the rules in: http://regexhero.net/tester (not mine nor am I affiliated with it :). Check the multiline option to test multiple paths.
So finally the rule should look like:
<match url="^((home|admin)(/|$))" />