Well, I'm incredibly egotistical so I won't answer that. I will however say that using someone else's code, even if they are a far better programmer than you, creates several additional areas of concern. You have to ensure:

• The code is not intentionally flawed.
• The code is not trojanned in transit or due to server compromise
• The original programmers are at least as competent as you at the task at hand
• There are no licensing issues (including maintenance issues)

I left out unintentional bugs although I've often found (keyword: found) far fewer in my code :). A much larger problem (especially in Perl) is style. I can read my code far, far easier than most other people's. I'm not talking about indentation, and unimportant/easily fixable issues here, but larger (mildly subjective) design issues. Often I've found it quicker to write a module than to read it, understand it, and do a quality assessment.

However, your point is obviously a valid area of concern. To an extent it is the same issue that I'm using perl instead of writing my own language (rest assured, it is in my todo.list). You could even take it down to the level that I should be creating all hardware and software from scratch (unfortunately I'm not that good... yet). There must be a level of trust, or more accurately an acceptable risk threshold, when dealing with any technology. I'm just a little more paranoid than most.

There are other advantages to this approach as well. If I had always just used existing tools and taken the easy way I don't think I would know half the things I do now. I also occasionally come up with something that improves upon the existing. And as crazy as it might sound, I also enjoy writing what is often considered tedious code (XML parsers, template systems, drivers). It's sort of a "well I haven't written project x yet, might as well go ahead." Or more articulately, as Richard Feynman once said "What I cannot create, I do not understand."

So yeah, I'm just babbling on now, I intended this to be a two sentence response, really :). So point taken, but there are a bunch of other things to consider, and even if they don't outweigh your point, it clears out a couple bytes of my memory needed for reinventing stuff :).