That's pretty inefficient as it will read in all of the matching lines from your input before it prints things out.

That aside, if you want to remove comments from all lines before printing and remove empty lines completely you probably want something more like this.

while( <INFILE> ) {
  chomp;
  s/^\s*#.*$//;
  next unless length $_;
  print OUTFILE $_, "\n";
}
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Update: As is remarked below, the s/// needs to be anchored. And yes, this skips empty lines. Now where's my caffeine . . .

That removes all empty lines, not just those that were comments. Fix:

while (<INFILE>) {
   chomp;
   next if /^\s*#/;
   s/\s*#.*$//;
   print OUTFILE "$_\n";
}
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The problem with s/\s*#.*$//; is that you might start breaking scripts unexpectedly. Given this (contrived but not unlikely) code snippet

my @fred = (1, 2, 3, 4, 5);
my $lastSub = $#fred;
print qq{$lastSub\n};
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running your substitution will result in

my @fred = (1, 2, 3, 4, 5);
my $lastSub = $
print qq{$lastSub\n};
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Perhaps something like

s{(?<!\$)#.*$}{};
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would be better but there may be other syntax where the hash is not the start of a comment that I haven't thought of.

Cheers,

JohnGG

Update: Found another non-comment occurrence of the # character in the colour values in Tk programs, e.g.

-background => #101010,
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so perhaps now

s{(?<!\$)#(?![0-9a-fA-F]{6}).*$}{};
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use List::MoreUtils qw( apply );

print OUTFILE apply { s/\s*#.*//; }
              grep  { !/^\s*#/ }
              <INFILE>;
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If you want to keep the lines that contained nothing but comments, remove the grep.

List::MoreUtils is not a core module, but it is a very useful module. It can be installed using ppm install List-MoreUtils if you're using ActivePerl.

Is there any way to do it without using any modules? (Just curious.)

Thanks!

huh, there's already a solution that doesn't use any modules in this thread.

But apply can be implemented using map pretty easily.

print OUTFILE map  { my $s = $_; $s =~ s/\s*#.*/; $s }
              grep { !/^\s*#/ }
              <INFILE>;
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You could even merge the map with the grep, but then it looks like spagetti.