Dear great perl masters, I've got this code which should send an AT-command to a serial port (with a modem behind that) and read the response from the modem. The sending of the command is working fine but I'm not getting any response in my loop. Do you maybe see the error and give me some advice?

    use IO::Socket;
    use IO::Select;

    my $COMport=33;

    while (1)
    {
        #open Port or die if blocked / wrong port
        if (!open( PORT, "+>\\\\.\\COM$COMport" ))
            {  
                die ("Can't open COM$COMport");
            }
            PORT->autoflush(1);
            PORT->flush();
            print "\nEnter AT command:";
            my $ATcmd=<STDIN>;
            chomp($ATcmd);         # remove CRLF
            $ATcmd =~ s/^\s+//;        # remove leading space
            $ATcmd =~ s/\s+$//;            # remove trailing space
            print "Sending: '$ATcmd'\n";
            print PORT $ATcmd . "\r\n";
        
            print "reading\n";
            #Reading the response
            while (my $ret=<PORT>)
            {   
                print $ret;
                if ($ret=~/^OK/ || $ret=~/^ERROR/) { last}
            }
            close(PORT);
    }

    print "done!";
[download]

Thank you in advance! Regards, Stefan

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