The “fat comma” 

use Test::More;

my @test_data = (
    'I'     => 1,
    'II'    => 2,
    'III'   => 3,
    'IV'    => 4,
    'V'     => 5,
);

while(@test_data) {
    my $input     = shift @test_data;
    my $expected  = shift @test_data;
    my $received  = test_func($input);
    is($received, $expected, $input);
}