Environment variables in PowerShell with a dot (.) in the name
To access any kind of PowerShell variable where the name contains non-alphanumeric characters, use the ${…} notation as in:
${env:variable.with.dots} = "Hi there"${env:variable.with.dots}
This works for variables in any drive (registry, filesystem, etc.)
Use the .NET method to get the variable:
[Environment]::GetEnvironmentVariable("FOO.BAR")