Thanks I should note that "text file busy" only happens after i open the pipe with my perl script and terminate it. After that, this error occurs irrespective of whether later i've got the script (reader) running together with the writer or a writer by itself.
I've checked the pipe is open by one thread only and the descriptor is not maintained after i exit the script.
The code snippet is quite basic:

my $alertsthr = threads->new(\&al_thread); 

$SIG{'INT'} = 'CLEANUP'; 
sub CLEANUP { 
    print "\nClosing pipe\n";    
    close PIPE; 
    exit(); 
}
 
sub al_thread 
{ 
  my $myline; 
  while (1) # keep reading from the pipe until we're killed 
  { 
      print "$config->{FIFO} open\n" if $config->{VERBOSE}; 
      open (PIPE, "$config->{FIFO}") or die "Could not open the input 
+pipe $config->{FIFO}\n"; 

      while($myline = <PIPE>) 
      { 
          print "read $myline\n" if $config->{VERBOSE}; 
          process_message($myline); 
      } 
      print "$config->{FIFO} EOF\n" if $config->{VERBOSE}; 
  } 
    
}
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