Speaking as someone who, as a matter of fact, "knows both languages quite well, thankye" ... I am never of the opinion that you will ever solve any real-world business problem by introducing another programming language into the mix.

If you write crappy code in Perl, then you will write crappy code in Python. And vice-versa.

Actually, the root cause of the problem is that people react favorably to software that is new, and they do not know how to properly maintain software that is old. Instead of learning how to do that, they simply want to sweep it away and start over.

You should immediately fire a programmer who advocates such a position. Every piece of new computer software very quickly becomes old.

If you are an undisciplined coder who writes crappy code, then you will do just that ... no matter what language(s) you are using. No characteristic of any language will keep you from doing that, just as no characteristic of any language will cause you to do that.