I worked as a freelance, writing simple programs for my clients.

[MikeNewYork]

Matthew, you can post all the dictionary examples you can find, but in many uses, commas are a matter of individual preference.

 

[Tdol]

Also, many dictionaries use sample sentences that are taken from real language usage, and may reflect the preferences of the writer. It doesn't automatically mean that the example sets the pattern for all usage- the sentence is normally given to illustrate a word of phrase in use.