Well, to start with, the shell command ls Dev*.txt > Dev.txt will put Dev.txt into Dev.txt, which is probably not intended.

Why bother using backticks if you're just going to print the answer anyway? You might as well use system, and save some interprocess communication (or use perl to construct the file list).

Why do you want to concatenate all the Dev*.txt files into res.txt anyway? t'ain't going to help you much (but the quick way to do it is cat Dev*.txt > res.txt). If you really want to find all files for words ending with three digits, then grep is more likely to be your friend.

Why do you want to do this anyway? Given the laborious number of steps you want to go through, I'd suspect this is homework, rather than a real world problem.

--
Tommy
Too stupid to live.
Too stubborn to die.