First, the caveats:
1) We're not likely to write your program for you, at least not without some more info and help from you.
2) If you don't know Perl, Perl may not be the right choice for you.

Now, something more useful.

For those of us who don't use CVS, give a brief description of what you're trying to do, without invoking CVS as an explanation.

Also, what operating system are you on? It may be that a simple shell or batch file will do what you want. For example:

rename CVS1 CVStemp
rename CVS2 CVS1
rename CVStemp CVS2
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