Short answer: Yes
Long answer: Copyrights protect works, and trademarks protect marks (i.e.,
a recognizable sign, design or expression which identifies products or services), so trademarks are what you should be concerned with when registering domains.
Since they're so widely used, the names of programming languages are typically in the public domain, unless developed as a proprietary language and trademarked (e.g., Microsoft's Visual Basic),
Although trademarks containing these names might be filed for specific products or services, that doesn't preclude using them in a domain name for other products or services, especially if they're not confusingly similar to other marks.
For example, "Perl" is trademarked in the U.S. by The Perl Foundation as:
Computer software for use in cross-platform software application,
software component and website development; computer software for use
in developing, analyzing, coding, checking and controlling other
computer software; and computer software that implements a procedural
and object-oriented programming language.
Providing that you do not utilize a domain that's named similarly to "Perl" for the same purpose as above in the U.S. (or other countries where it's trademarked), then The Perl Foundation would not be able to demonstrate that you're infringing upon their mark.
Perl.com which discusses the uses of Perl, is registered by another party, and so is
Ruby.com are not associated with their respective programming language either.
In summary: Just make sure that your domain names are not confusingly similar to trademarks and the products or services they're registered for, in the country in which they're registered, and you should be fine. If you have any other concerns, contact a lawyer who specializes in patent & trademark law.