May I suggest trying the documentation again? CGI.pm is exceedingly well documented. The examples you copied are highly incorrect. In particular:

my $filename = "text.txt";
binmode($filename);
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Calling binmode on a string doesn't do anything useful -- it only does something interesting on filehandles.

while (<$filename>) {
       print;
}
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Attempting to read from a string doesn't do anything useful -- it's a symbolic reference, but since you don't open a filehandle anywhere called 'text.txt', you won't get any data.

while ($bytesread=read($filename,$buffer,1024)) {
       print OUTFILE $buffer;
       print "the thing is open";
}
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Again, $filename isn't a filehandle or even a symbolic reference to a filehandle. Even if it were, you'd have read everything from it in the while loop above. Besides that, mixing buffered reads with unbuffered generally mixes things up.

The CGI documentation is *really* good about explaining how to receive uploaded files. It's well-worth your time to figure out how to read it rather than trying to copy and paste several other scripts together. That's obviously not working here. Why not try something different?