making smart domain general 301 redirects for moved pages using .htaccess - apache

Question

I found my server's c-panel produced code of the following form when I defined redirects using it's web gui. This works fine. However I'm concerned that I could write this much more efficiently, more generally and hopefully with less repetition.
RewriteCond %{HTTP_HOST} ^domain\.com$ [OR]
RewriteCond %{HTTP_HOST} ^www\.domain\.com$
RewriteRule ^some/unwanted/uri$ "http\:\/\/www\.domain\.com\/some/improved/uri" [R=301,L]
RewriteCond %{HTTP_HOST} ^domain\.com$ [OR]
RewriteCond %{HTTP_HOST} ^www\.domain\.com$
RewriteRule ^someother/unwanted/uri$ "http\:\/\/www\.domain\.com\/someother/improved/uri" [R=301,L]
repeat x20
I understand from Jon Lin's answer that repeating the following would usually be necessary.
RewriteCond %{HTTP_HOST} ^domain\.com$ [OR]
RewriteCond %{HTTP_HOST} ^www\.domain\.com$
However hjpotter92 has suggested shortening that to:
RewriteCond %{HTTP_HOST} ^(www\.)?domain\.com$
This is definitely an improvement but how can it be made domain general too. Could that be written as follows to apply to apply more generally to test.domain.com too?
e.g.:
RewriteCond %{HTTP_HOST} ^(*\.)?domain\.com$
I also understand from Jon Lin's answer that I could also replace the following in my code
"http\:\/\/www\.domain\.com\/some/improved/uri" [R=301,L]
with:
"/some/improved/uri" [R=301,L]
Which is gladly both shorter and more general.

Answer 1

Is there any need to keep repeating the following?
Yes, rewrite conditions only apply to the immediately following rule, so any following rules won't have those conditions be applied.
It's not really that inefficient to repeat the conditions, since the conditions aren't even checked unless the rule's pattern matches. That means given this rule:
RewriteCond %{HTTP_HOST} ^peterliddle\.com$ [OR]
RewriteCond %{HTTP_HOST} ^www\.peterliddle\.com$
RewriteRule ^work/cornwall/cornwall_early$ /redirect-target [L,R=301]
If the URL was /blahblah, the rewrite engine first tries to match that URL against the rule's pattern, and since it doesn't match ^work/cornwall/cornwall_early$, the whole rule is skipped, the conditions don't even need to be considered.
If it's a matter of being hard to read, you could have a rule at the very top that bypasses all rules in your htaccess file if those conditions are not met. For example:
RewriteCond %{HTTP_HOST} !^(www\.)?peterliddle\.com$ [NC]
RewriteRule ^ - [L]
RewriteRule ^work/cornwall/cornwall_early$ http://www.peterliddle.com/work/cornwall/cornwall_58-65 [R=301,L]
RewriteRule ^work/cornwall/cornwall$ http://www.peterliddle.com/work/cornwall/cornwall_66-69 [R=301,L]
RewriteRule ^work/whale_moor_a/a_first$ http://www.peterliddle.com/work/whale_moor/lakeland_hills [R=301,L]
So if the conditions for the HTTP HOST fails, the rules are completely bypassed. Problem with doing things this way is you'd have to add any new rules that you don't want the conditions to be applied above these rules.
You can also remove the http://www.peterliddle.com part from your rule's target, since you've already tested for the same domain in the HTTP_HOST.

Answer 2

Following kind advice on stack overflow, testing and some reading I settled on a list of rewrite rules following of the form:
RewriteCond %{HTTP_HOST} (^|\.)domain\.com$
RewriteRule ^some/unwanted/uri$ "/some/improved/uri" [R=301,L]
N.B. The following snippet does not work. It crashes the site and is not recommended.
RewriteCond %{HTTP_HOST} ^(*\.)?domain\.com$
The following seams to work across all subdomains. Therefore I can test in test.domain.com and then use the same .htaccess file in www.domain.com and have greater confidence it will work without having to make further changes to the code.
RewriteCond %{HTTP_HOST} (^|\.)domain\.com$