...unless I do not understand what you mean with write.

The line in question is:

print READ "is empty!\n";
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This syntax has the form print FILEHANDLE LIST, as documented in print, and it says: print the string “is empty!”, followed by a newline, to the filehandle READ. But, as I pointed out, the READ filehandle has been opened for reading (input), not writing (output). The only reason you are not seeing this die is that the files you are testing aren’t empty, so the condition never evaluates to true and the print statement is never actually called.

You probably meant to write just print "is empty!\n"; which is equivalent to print STDOUT "is empty!\n";, but you should also consider using warn "is empty!"; which is equivalent to print STDERR "is empty!\n"; (see warn).

Hope that helps,