Can't turn off buffering in Perl using $|=1;

Question

I am writing to two files, one a log using a Log_message function and the other within my file_write function writing to OUT and I want to write it line by line and not be buffered so that it writes line by line and not all in one go at the end of the script.

I have read about buffering and making the filehandle hot but can't get my code to work.

In this example I have added the $|=1; just before the foreach loop but it still writes in one go. Am I doing something really dumb?

I have enclosed my entire script further down if that helps.

    #-----------------------------------------------
    sub file_write {
    #-----------------------------------------------
    open OUT, ">>$OUT" or Log_message ("\n$DATE - $TIME - ERROR - Could not create filelist.doc \t");
    Log_message ("\n$DATE - $TIME - INFO - Opened the output file");
    my $total = scalar keys %{ $doc->{ resource } };
    Log_message ("\n$DATE - $TIME - INFO - Found: " . $total . " resources");
    #printf "resources: %s\n", scalar keys %{ $doc->{ resource } }; 

   $|=1;

    #And I have also tried:

    #use IO::Handle;
    #STDOUT->autoflush(1);

    foreach ( keys %{ $doc->{ resource } } ) {
        #print OUT $doc->{ resource }->{ $_ }->{ id }, "\n";
        my $ID = $doc->{ resource }->{ $_ }->{ id }, "\n";
        Log_message ("\n$DATE - $TIME - INFO - Found: " . $ID);
        my $testurl = "http://dronlineservices.letterpart.com/web/content.xql?action=doc_html&lang=en&pub=" . $pubId . "&docid=" . $ID;
         print OUT "$testurl\n";
      sleep 1;

    }

And the entire script

#   !c:/Perl/bin/Perl.exe


#-----------------------------------------------
#Modules
#-----------------------------------------------
use XML::Simple;
use LWP;
use Data::Dumper;
$Data::Dumper::Indent = 1;
$Data::Dumper::Sortkeys = 1; 
use strict;
use warnings;

#-----------------------------------------------
#Declare variables
#-----------------------------------------------
    my $script = "LiveContent Auto Cache Script";   # Name of the script
    my $version = "Version 0.1";
    #my $pubId = "COMP-20110922XXXX";
    my $pubId = "LiveContentDoc";       
    my $OUT = "output.txt";
    my $LOG = "cacher-log.log";     # Location of log file
    my $DATE;                                                   # Date in form 2001-sep-01
  my $DATENR;                                               # Date in form 2001-01-09 
  my $TIME;                                             # Time in form 12:04:03
  my $txtmesg = "";
  my $resource;
  my $xs;
  my $doc;

####################################
########### Main Program ###########
####################################
error_logger();                             # Open Log file and time stamp it
request_url(); #Open the xml url and read it in
file_write();  #write the contents of the xml url to a file


#-----------------------------------------------
sub request_url {
#-----------------------------------------------
my $useragent = LWP::UserAgent->new;
my $request = HTTP::Request->new( GET => "http://digitalessence.net/resource.xml" );
#my $request = HTTP::Request->new( GET => "http://dronlineservices.letterpart.com/web/content.xql?action=index&lang=en&pub=" . $pubId );
$resource = $useragent->request( $request );  
$xs         = XML::Simple->new();
$doc        = $xs->XMLin( $resource->content );

}


#-----------------------------------------------
sub file_write {
#-----------------------------------------------
open OUT, ">>$OUT" or Log_message ("\n$DATE - $TIME - ERROR - Could not create filelist.doc \t");
Log_message ("\n$DATE - $TIME - INFO - Opened the output file");
my $total = scalar keys %{ $doc->{ resource } };
Log_message ("\n$DATE - $TIME - INFO - Found: " . $total . " resources");
#printf "resources: %s\n", scalar keys %{ $doc->{ resource } };



use IO::Handle;
STDOUT->autoflush(1);

foreach ( keys %{ $doc->{ resource } } ) {
    #print OUT $doc->{ resource }->{ $_ }->{ id }, "\n";
    my $ID = $doc->{ resource }->{ $_ }->{ id }, "\n";
    Log_message ("\n$DATE - $TIME - INFO - Found: " . $ID);


    my $testurl = "http://dronlineservices.letterpart.com/web/content.xql?action=doc_html&lang=en&pub=" . $pubId . "&docid=" . $ID;
     print OUT "$testurl\n";


        #   my $browser = LWP::UserAgent->new;
        #   $browser->timeout(240);
        #   $browser->env_proxy;
        #   $browser->agent('Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)');

            # my $response = $browser->get($testurl);

        #    if ($response->is_success) {
             #     print "\n############################\n";
             #     print "$testurl\n";
             #     print "\n############################\n";
              #   print $response->decoded_content;  # print the response out
            # }
            # else {
             #    my $error = $response->status_line;
            #     Log_message ("\n$DATE - $TIME - WARN - Can't load $ID because: $error");
             #    die $response->status_line;

        #   }



    #my $loadrequest = $ua->get('http://dronlineservices.letterpart.com/web/content.xql?action=doc_html&lang=en&pub=" . $pubId . "&docid=" . $ID');
    sleep 1;

}


Log_message ("\n$DATE - $TIME - INFO - Written the output file");
#close(OUT) or Log_message ("\n$DATE - $TIME - WARN - Failed to close the Output file");
Log_message ("\n$DATE - $TIME - INFO - Closed the output file");
}
#-----------------------------------------------
sub error_logger {
#-----------------------------------------------
    time_stamp();                                                                                                                               # Run Time stamp sub
    open LOG, ">>$LOG" or die ("could not open log file <$LOG>");                               # Open Log File
    Log_message ("\n$DATE - $TIME - -----------------------------------------\ \t");
        Log_message ("\n$DATE - $TIME - INFO - Start of Application\ \t");
        Log_message ("\n$DATE - $TIME - INFO - $script\ \t");
        Log_message ("\n$DATE - $TIME - INFO - $version\ \t");
        Log_message ("\n$DATE - $TIME - -----------------------------------------\ \t");

}
#-------------------------------------------------------------
sub Log_message {
#-------------------------------------------------------------
    time_stamp();                   # Run time_stamp every time the log is written to
    my($mesg) = @_;
    print LOG $mesg if $LOG;    # Print to log file
    print $mesg;              # Print to Screen
    $txtmesg = $mesg;
    #print "\nLOGGING: $txtmesg\n";
} 
#-----------------------------------------------
sub time_stamp {
#-----------------------------------------------
    my($Sec,$Min,$Hour,$Day,$MonthNr,$Year) = localtime(time());
    my $Month=("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")[$MonthNr];
    $Sec = sprintf("%02d",$Sec);
    $Min = sprintf("%02d",$Min);
    $Day = sprintf("%02d",$Day);
    $MonthNr = sprintf("%02d",++$MonthNr);
    $Year = 1900 + $Year;
    $DATE = "$Year-$Month-$Day";
    $DATENR = "$Year-$MonthNr-$Day";
    $TIME = "$Hour:$Min:$Sec";
} # end sub

Answer 1

You forgot to select the handle first.

select( (select(OUT), $| = 1)[0] );

Answer 2

use IO::Handle;
OUT->autoflush(1);

But it is better to use lexical filehandles:

use IO::Handle;
open my $outfh, ">>", $OUT or Log_message ("\n$DATE - $TIME - ERROR - Could not create filelist.doc \t");
$outfh->autoflush(1);