# Open both IN_FILE and OUT_FILE here!

while(<IN_FILE>) {
   chomp;
   next unless length;
   print OUT_FILE "$_\n";
   }

##</code><code>##

open (INFILE, "input.txt");
open (OUTFILE, ">output.txt");

while (INFILE) {
$_ =~ s/foo/bar/gms;
print OUTFILE "$_\n";
}