You have

use warnings;
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at the top of your program.

When you run your program, Perl will tell you at least one problem in your program immediately:

perl -wle 'open my $fh, "<", "test.txt"; print $fh "hello"'
Filehandle $fh opened only for input at -e line 1.
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If you don't get this output, please either post the real code you are using or find a way to see the output of your program.