It would also have to take into account how many prisoners in jails are innocent -- there's bound to be a correlation between the two attributes. :D

But seriously... are you trying to assert that no one has ever written evil code in Perl? Perhaps Perl has a better proportion of benevolent vs. evil code released to the world, compared to other languages (e.g. Visual Basic, x86 assembler, javascript), but I don't know how someone could possibly measure that.