I don't like this for the following reasons:

• You are reading the whole file in memory TWICE! Once for the arguments to the foreach and another one when pushing everything into @data. In any case, you want to use while instead of foreach.
• You are overwriting the file in place, without creating a backup. What if the machine crashes in the middle of the "print FILE @data"? You have lost your data.

I personally like the technique of writing the results to a new temporary file, and then renaming the original to a backup name and the temporary file to the original. Something like this:

open FILE, "/path/to/file" or die "$!\n";
open OUT, "/tmp/tmpfile.$$" or die "$!\n";
while(<FILE>) {
  next if /^\s*$/;
  print OUT, $_;
}
close FILE; close OUT;
rename("/path/to/file", "/path/to/file.bak")
  or die "Error in rename: $!\n";
rename("/tmp/tmpfile.$$", "/path/to/file")
  or die "Error in rename: $!";
[download]

Side note: using "/tmp/tmpfile.$$" as a temporary file name could have security implications if the program is running set-uid. For better ways of creating a temporary file name, see the FAQ How do I make a temporary file name?

Also, a regex is not necessary if you are looking for strictly empty lines. But many times, a line is considered empty even if it contains white space, in this case using regular expressions is the best way to do it.

--ZZamboni

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