Getting variables from a string

[filburt1]

Let's say I have a string that contains "This has a $var1 and $var2" (ignore escaping the $ for now). How can I find out what variable namess are in the string? I'm defining a variable name as everything from the leading $ to an illegal variable name character, including array braces ([]).

I know it probably involves regular expressions but I don't know anything about them.