Welcome to the Monastery, Coop197823!

Always use strict; and use warnings;, and you should also include a sampling of your input for testing (put that in <code></code> tags like you've done with your code), along with a snip of your expected output. Does the following do what you expect?

#!/usr/bin/perl
use warnings;
use strict;

if ($ARGV[0] && ! $ARGV[1]){
    die "Usage: ./script.pl file1.txt file2.txt\n";
}

my $file1 = $ARGV[0] || 'in.txt';
my $file2 = $ARGV[1] || 'in2.txt';

my %names;

# file 1

open my $fh1, '<', $file1
  or die "can't open file $file1: $!";

while (<$fh1>) {
    next if /^\s*$/;
    $names{(split)[0]} = 1;
}

close $fh1 or die $!;

# file 2

open my $fh2, '<', $file2
  or die "can't open file $file2: $!";

while (<$fh2>) {
    print if /^(\S+)/ && not $names{$1};
}

close $fh2 or die $!;
[download]

You can call it like ./script.pl file1.txt file2.txt. If you leave off the arguments, it'll use the defaults provided. If you have one argument but not both, the script will fail.

-stevieb

edit: added check for blank and whitespace-only lines, added @ARGV.