Typically, when you hit Enter in a smart editor, it copies the indentation of the last line by inserting the same amount of spaces, so if you don't delete them, the code looks like this:
sub sum {
my @numbers = @_;
 
my $sum = 0;
foreach (@_) {
$sum += $_;
}
 
return $sum;
}
(Yes, the example is silly; that sub could be written in two or three lines. :))
To be honest, these lines make my cursor feel dizzy, so I tend to clear them out. (I admit, that this behavior generates commit noise + inconsistency.) Plus, the whitespace are unnecessary bytes. Well, probably none of these does matter, at least in most obvious ways. So I wonder if there is any better (i.e. less subjective and less over-pedantic) reason why the lines should be blanked (by s/^\s+$//).
Note: And please try not to point me to the style guide. Imagine I'm the one writing the style guide: should I inherit rule "delete the extra spaces" or just bravely fight my intuition and leave those peaceful \t's and 's alone?. Or I just want to improve my "own" guide, which I can use where "official" guide is silent or missing.