I have found through experience that those two steps help people catch a very large portion of their common mistakes. In the event that you don't catch your error, the effort will make it tremendously easier for me (or anyone else) to read your code and offer more specific suggestions.

    sub login {
      $/ = "\015\012";
      print $client "username:";
      $login=<$client>;
      chomp $login;

      if ($login eq "") {
        print $client "Must enter a username!\n\r";
        &login;
      }

      $/ = "\012";
      open (FILE1, "users.txt") || print "Error occured while opening 
+file";
      while (<FILE1>) {
        ($first,$second ) = split /:/;
        print $first;
        if ($login eq $first) {
          print $client "Sorry this username has been taken, try again
+!\n\r";
          &login;
        }
        $/ = "\015\012";
      }

      close (FILE1);
      ...
[download]

What this highlights quite clearly, is that you're resetting $/ whilst you're still reading the file. Try moving it to outside the loop.

In addition, if it doesn't like the value it's found, then it's going to call &login again, while the file is still open. Which means that the file will be reopened, and $/ set inside a recursive call, then closed and reset when that recursive call ends. Not good thing.

In fact, the logon subroutine doesn't finish until 7 lines from the end of the script, containing the password subroutine on the way. Not good at all

If you run perltidy over it you will also notice that the indentation seems odd - it never returns to the left margin. This is because you are one } short which perl notes as this script does not actually compile.

#!/bin/perl
use IO::Socket;
use IO::Select;
$/                = "\015\012";
$nconnections_new = 0;
$login            = "";
$maxconn          = SOMAXONN;
$local            =
  IO::Socket::INET->new( Proto => "tcp", LocalPort => "1234",
    Listen => $maxconn, Reuse => 1 ) or die "Can't open socket\n";
while ( $client = $local->accept ) {
    $client->autoflush(1);
    &start;

    sub start {
        print $client "This is a test BBS!\n\r";
        print $client "(C)reate new user      (L)ogin";
        print $client "\n\r";

        my $option = <$client>;
        chomp $option;
        $option = "\U$option\E";

        if ( $option eq "C" ) {
            print $client "<<<Create new user>>>\n\r";
            print $client "Login must be at least 6 characters.\n\r";
            &login;
        }

        elsif ( $option eq "L" ) {
            &logon;
        }

        else { &start; }

        sub login {
            $/ = "\015\012";
            print $client "username:";
            $login = <$client>;
            chomp $login;

            if ( $login eq "" ) {
                print $client "Must enter a username!\n\r";
                &login;
            }

            $/ = "\012";
            open( FILE1, "users.txt" )
              || print "Error occured while opening file";
            while (<FILE1>) {
                ( $first, $second ) = split /:/;
                print $first;
                if ( $login eq $first ) {
                    print $client
                      "Sorry this username has been taken, try again!\
+n\r";
                    &login;
                }
                $/ = "\015\012";
            }

            close(FILE1);

            if ( length($login) > 7 ) {
                print $client "Your username was longer than 6 charact
+ers!\n\r";
                &login;
            }

            $pass = password();

            sub password {
                print $client "Password:";
                $password = <$client>;
                chomp $password;
                print $client "\n\rRe-enter password:";
                $password2 = <$client>;
                chomp $password2;
                if ( $password ne $password2 ) {
                    print $client "Passwords do not match, try again!"
+;
                    &password;
                }
                return $password;
            }

            open( FILE, ">>users.txt" )
              || print "Error occured while opening file";
            print FILE "$login:$pass\n";
            close(FILE);
            print "File written..\n\r";
            exit;
        }
    }

    sub logon {
        print $client "test";
    }

    close $client;
[download]

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

#!/bin/perl

use strict;
use warnings;
[download]