Why use Text::CSV? It's slower and it's broken. If you have Text::CSV_XS, use it. It's faster and it's not broken. In any event, here's one way (untested):

my $CSV_CLASS = $boolean ? $module1 : $module2;
eval "use $CSV_CLASS";

if ($@) {
    croak "Could not use $CSV_CLASS: $@";
}

my $csv = $CSV_CLASS->new;
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Cheers,
Ovid

Looking for work. Here's my resume. Will work for food (plus salary).
New address of my CGI Course.