You should try to make a little bit of effort to arrive at a solution on your own, at least say "This is what I've tried but it doesn't work and I don't know why".

Your task can be solved by reading the file in a loop, using split on each line and then putting the first returned element into a hash as a key (for example $hash{$element}=1. After you read the whole file you can open another file for writing and do

for my $name(keys %hash) {
  print $filehandle "$name\n";
}
[download]

Try to solve it with that information and do come back and ask if you have problems.