The OP was about avoiding silly programming mistakes. The responses given do that. The OP has since clarified the question, but that doesn't change the usefulness of the initial responses.

I use Perl in order to avoid classes of potential errors, such as dangling pointers. I use certain modules (such as DBI) to avoid other classes of potential errors (such as SQL injection). Then, there are the ways to improve using Perl to avoid other classes of errors (such as = in a conditional test vs. ==). After that, there is experience which is what the OP was attempting to ask for. That's what my response addresses.

As for this thread . . . have you ever tried to explain something to someone 10 years younger than you? That feeling of "Why can't you just understand the deeper subtleties" is what we're feeling right now with regards to your responses.