my $names_file = "code.txt";

open(NAMES, $names_file || die "Could not open file!");
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Because of the high precedence of the  || operator die will never be called because $names_file is always true.

You need to either use parentheses in the proper place:

open(NAMES, $names_file) || die "Could not open file!";
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Or use the lower precedence  or operator:

open NAMES, $names_file or die "Could not open file!";
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