How do I pass multiple parameters into a function in PowerShell?

Parameters in calls to functions in PowerShell (all versions) are space-separated, not comma separated. Also, the parentheses are entirely unneccessary and will cause a parse error in PowerShell 2.0 (or later) if Set-StrictMode -Version 2 or higher is active. Parenthesised arguments are used in .NET methods only.

function foo($a, $b, $c) {
   "a: $a; b: $b; c: $c"
}

ps> foo 1 2 3
a: 1; b: 2; c: 3

The correct answer has already been provided, but this issue seems prevalent enough to warrant some additional details for those wanting to understand the subtleties.

I would have added this just as a comment, but I wanted to include an illustration--I tore this off my quick reference chart on PowerShell functions. This assumes function f's signature is f($a, $b, $c):

Thus, one can call a function with space-separated positional parameters or order-independent named parameters. The other pitfalls reveal that you need to be cognizant of commas, parentheses, and white space.

For further reading, see my article Down the Rabbit Hole: A Study in PowerShell Pipelines, Functions, and Parameters. The article contains a link to the quick reference/wall chart as well.