my $infilename  = 'infile.txt';
my $outfilename = 'outfile.txt';

open my $infile, "<$infilename" or die "Unable to open $infilename $!";
open my $outfile, ">$outfilename" or die "Unable to open $outfilename $!";
while (<$infile>) {
  s/hue/someword/g;
  print $outfile $_;
}

close $infile;
close $outfile;