All-knowing monks

I have these two routines; 
sub getFile {
   my $fileName = shift(@_);
   unless ($gotFiles->{$fileName})
     {
      undef $/;
      open $file, $fileName;
      my $buf = <$file>;
      close $file;
      $gotFiles->{$fileName} = $buf; 
     }
   return $gotFiles->{$fileName};
  }

sub writeFile {
   my $data = shift(@_);
   if ($data =~ m@<filename>(.*?)</filename>@s) { $filename = $1; }
   if ($data =~ m@<data>(.*)</data>@s) { $filedata = $1; }    

   open(DAT,">$ENV{DOCUMENT_ROOT}/$filename") || return 0;
   print DAT $filedata; 
   close(DAT);
   $gotFiles->{"$ENV{DOCUMENT_ROOT}/$filename"} = $filedata;
   return 1;
  }

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My question is, how should I modify these in order to avoid lockups when multiple users are attempting to read/write the same files? is there some way perhaps to shunt off the writing to a background process?

In reply to file reading / writing collisions by simonodell

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