What else are they doing besides writing code that takes 5 days? Are they doing the design, documentation, informal tests to see if it works?

The other question to ask is, how thoroughly tested is the code? Devel::Cover can tell you how much of your code has been tested. To test really obscure conditions might require more time than it is worth but have testing coverage for 85% of your code might be considered a reasonable condition for the testing code is thorough enough.

For me, I have a ratio of about 2.5(hour) testing to 1(hour) programming. However, I am not spending time writing simple tests that I will not keep. A large part of my tests are written while I am designing the interface. So there is alot of intermingling of design, and tests with actual coding.

Coding is easy, testing code takes time because you need to verify the results and check to see where it is breaking. Programmers are doing testing, however most don't follow a formal system which their tests are documented and are repeatable. So don't be suprised if your coder is really spending 1 day in design, 1 day coding, 1 documenting, and 2 days testing.