open (IN,"<" . "c:/tmp.txt") or die "Doh: $!"; # Use ()'s, and added or die... sometimes that comes in hand when debugging.

while(<IN>){  # $_ is set to each line for each file.
  my $line = $_; # Take raw form of line
  $line =~ chomp $line; # chomp the line.
  if (length($line)){ # does line have non zero length?  (Sorta what you're doing.)
     print "$line\n"; 
  }
}
close IN; # Clean up.