With the release of Text-CSV_XS 0.35 (Valloire), I think I have addressed the undef question enough to be really useful:

> perl -MData::Dumper -MText::CSV_XS -l \
       -e 'my $csv=Text::CSV_XS->new ({ blank_is_undef => 1 });' \
       -e '$csv->parse (q{1,,"", });' \
       -e 'print Dumper$csv->fields'
$VAR1 = '1';
$VAR2 = undef;
$VAR3 = '';
$VAR4 = ' ';
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