open(DATA,"$file") || die "cannot read the file: $!";

I think if you change this to

open(DATA,"$file") || die "cannot read $file: $!";
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you can narrow down the problem considerably ;-) And for the safe side, I suggest you are using open(DATAFH,'<',$file), since DATA is a "reserved filehandle" in Perl (like STDIN or STDERR), and the 3-argument open is safer anyway, if the file to be opened is stored in a variable.