This is brought up now and then on Slashdot. Treating programming languages like something actually hard to learn.
Specific programming languages are irrelevant.
Programming paradigms and levels are relevant. But if you know a language in one paradigm, it's easy to learn another one. If you know C, the step to Python is fairly close. Lisp or Erlang is a little more distant, but it's not impossible far to learn in a few weeks.
If you can't pick up the basics of any computer language in a few weeks, I get the impression you're not really sure of what you're doing.
So it's irrelevant if you already know the language. Except for very confused recruiters. The question is, can you get good at the skills needed at the job within a few weeks? You wont know the projects or the libraries in the new company anyway, picking up a new computing language isn't going to be the hard part.
But then again, ASN.1 isn't a programming language more then TCP/IP is a programming language, so maybe the question is more confused than that.
(Languages I have encountered in my professional career: V2 BASIC, 6510 assembler, ABC8* BASIC, dBase 4, x86 assembler, 680x0 assembler, Batch files, Pascal, C, C++, Shellscripts, Pike, ECMAscript, Java, Flash, ARM assembler, and Python. In that order. I have done ASN.1 in the form of SNMP, but I really don't think I would call it a programming language.)