G'day scripter87,

You haven't really provided sufficient information. "it works" and "it dont" and spectacularly useless error reports. You haven't shown how you're testing this: i.e. what you're using for input. You haven't shown your data: there could be line ending and embedded whitespace issues. A better question gets better answers: take a look at the guidelines in "How do I post a question effectively?" to see how you can achieve this.

There's issues with the code as posted. It will print "not valid" for every record in names.txt until it either finds a match or reaches EOF. I see Eily pointed out an issue with $names: you said this was a typo; if you copy and paste your actual code, this won't happen. Do you really want to open/read/close the entire file for every "my $input = <STDIN>;"? Do you allow more than one attempt?

Here's a potentially better way to do what you want:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

my $name_file = 'names.txt';

open my $name_file_fh, '<', $name_file;
chomp(my @names = <$name_file_fh>);
close $name_file_fh;

print 'Enter login name: ';
chomp(my $input = <STDIN>);

print "Invalid!\n" unless grep { $_ eq $input } @names;
[download]

Note that you can wrap the 'Enter login name: ' part in a loop to allow multiple attempts without having to reread the file. Not shown in your posted code, so I haven't tried to make guesses here, but you'll need to code some sort of successful login actions.

Update: Prompted by Eily's mention of a hash and exists, which I saw after posting, this would be an improvement on what I originally provided:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

my $name_file = 'names.txt';

open my $name_file_fh, '<', $name_file;
my %name = map { chomp; $_ => 1 } <$name_file_fh>;
close $name_file_fh;

print 'Enter login name: ';
chomp(my $input = <STDIN>);

print "Invalid!\n" unless exists $name{$input};
[download]

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