open my $fh,'>',$file_name || die "can't open $file_name for writing: 
+$!\n";
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No..either:

open my $fh,'>',$file_name or die "can't open $file_name for writing: 
+$!\n";
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Or:

open(my $fh,'>',$file_name) || die "can't open $file_name for writing:
+ $!\n";
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And similar for your other uses of the "||" operator.