Does chomping @data_names help?

@data_names = <JOE>;
chomp @data_names;
# . . .
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Your file names probably don't have newlines at the end.

Your loop could be written more perlishly as

for (@data_names) {
    # $_ contains each name in turn
}
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There is nothing wrong with re-using a file handle as you do. It's customary nowadays to use a lexical handle and 3-arg open,     open my $fh, '<', $_ or die $!;