Use of LE is deprecated

Jonathan has asked for the wisdom of the Perl Monks concerning the following question:

hmmm Ok, this modest script doesn't compile

#!/usr/local/bin/perl -w
use strict;
open LE, "<y" or die "can't open y: $!";
close LE;
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Use of LE is deprecated at x line 3.
Not enough arguments for open at x line 3, near "open LE"
syntax error at x line 3, near "LE,"
Use of LE is deprecated at x line 4.
syntax error at b line 4, near "LE;"
Execution of x aborted due to compilation errors.
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It looks like using the uppercase version of any of the string comparison operators as a file handle name will fail.

It's not a big deal but Google didn't help and I would like to know why this happens?

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