Hi johnrcomeau,
Really, I can't figure what you really wanted to use, however you can use this: [the code below actually works]

use warnings;
use strict;
use Excel::Writer::XLSX;

func(@ARGV);

sub func {
    my $file      = 'perl.xlsx';
    my $book      = Excel::Writer::XLSX->new($file);
    my $worksheet = $book->add_worksheet();
    my $closure_workbook;
    if (@_) {
        $closure_workbook = sub {
            $worksheet->write_col( 0, 0, [@_] );
        };
        return $closure_workbook->(@_);
    }
    else {
        $worksheet->write( 0, 0, 'Hi Excel!' );
    }

}
[download]