The syntax is elsif not elseif. You need an else clause otherwise if the cost is >80 you get free (undef probably) shipping.....

for ( my $total_price = 10; $total_price < 100; $total_price += 10 ) {
    if ($total_price < 20.00) {
        $ship_price = 3.50;
    }
    elsif  (($total_price >= 20.00) && ($total_price < 50.00)) {
        $ship_price = 5.50;
    }
    elsif (($total_price >= 50.00) && ($total_price < 80.00))  {
        $ship_price = 10.50;
    }
    else {
         warn "that's expensive!\n";
        $ship_price = 15;
    }
    
    my $grande_costa = $total_price + $ship_price;
    print <<STUFF;
Total price: $total_price
Shipping:    $ship_price
Grand Total: $grande_costa

STUFF

}
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cheers

tachyon

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