When selecting a programming language (such as C++, Perl, Python) or solving platform (such as Mathematica, Pari) there should be little deliberation as to which to use. Sometimes the choice is based on application, other times it may be a choice of convenience or development time.
Many use Project Euler as a platform for exploring new languages and others just want to see how fast they can successfully arrive at the answer. Some may even find the answer to a problem searching the Internet with Google or looking around the libraries of integer sequences.
All’s fair when trying to solve a problem as long as attention can be placed on repeatability, understanding and extensibility. That is to say that a program would serve nicely to solve more complex questions in the same vein as the original problem and still perform under the requirements of the Project (1 minute rule, for example).
With that said, we have ventured forth and written many programs in Python and C++ only because Perl’s source was highly obfuscated or its performance unable to provide an answer in the allotted 1 minute time limit.