Agree that researchers are not forced to use one particular language. The choice of programming language and tools is almost free when working alone. However, when working in groups that share code it is more difficult to freely choose. Nowadays, it can be almost impossible be the only one using Perl while all others code in Python or R, unless the particular workflow and local culture allows it. For example if only exchanging data chunks in some standard format, instead of code. I believe that the major barrier to widespread use of Perl is that it has largely been displaced by Python and R in the general culture of scientific circles. Technical details or idiosyncrasies are weak arguments often used in discussions, but I believe the real thing is just cultural.