Since it looks like you're tidying up html, perhaps HTML::Tidy could be of help to you.

Also, perl -p -i -e ' s/^\s+//; s/[^\S\n]+$//;' *.shtml will do as you ask.

• -i do inplace editing of files. opens STDIN and STDOUT to file(s) listed
• -e run this code
• -p stick each line of your files (listed in @ARGV) into $_ and print $_ back out after your -e'ed code

perlrun tells more on these

and the -e does these things

s/^\s+//;       # strip leading whitespace
s/[^\S\n]+$//;  # strip trailing whitespace
[download]

I'm not sure which part of this is removing the all whitespace lines but it does appear to be happening <_<

Update ofcourse! the all-whitespace lines (including thier \n) is being removed by the first regex!

Update to make a little more sense