die "Usage: $0  infile outfile\n" unless ( @ARGV == 2 );
my $infile = shift;
my $outfile = shift;

open( INPUT, '<', $infile ) or die "$infile: $!\n";
open( OUTPUT, '>', $outfile ) or die "$outfile: $!\n";

while (<INPUT>) {
    # do stuff with $_;
    # print something to OUTPUT
}