Power of Comma (,)

I leave my money to Jamie, Heidi and Mark.
I leave my money to Jamie, Heidi, and Mark.

Though assigned least preference in C language operator list, ',' is one of the most crucial marker in English language.
See the power by yourself by reading those two lines.

First one means:
Jamie gets 50%
Heidi and Mark gets 25% each.

Second one means:
Each gets 33%.