What's so wrong with doing open RD, '<', 'file.txt' ?

I was involved with two discussions about this recently, lexical vs. local file handles and Re^2: Summing numbers in a file, so here are my two cents. To summarize the disadvantages of bareword filehandles:

• They don't protect against typos.
• They're package-globals.
• They clash with package names and subs.
• If you do want to localize them, that comes with even more disadvantages.
• Package-global filehandles usually go out of scope much later than lexicals, so the automatic close doesn't really help.

I don't think that bareword filehandles should "never, ever" be used, and removing them would most likely break a lot of CPAN. But IMHO they shouldn't be used in new code, and newcomers should use lexicals instead. My understanding of Perl 7 is that it is an attempt to introduce defaults that are modern and reduce the cognitive load on the coder - sure, you can use bareword filehandles if you know what you're doing and are willing to manually check for all potentially typos and name clashes caused by them. In the beginning, I used to code without strict and warnings, and I can still remember the amount of time I would spend proofreading my code for such issues.

use of barewords as filehandles will be disallowed in perl 7

My understanding of Sawyer's talk is that the new default will be no bareword::filehandles, and you are free to write use bareword::filehandles.