It appears that the ${file} variable can be used in launch.json configurations to determine the "program" to be run when the user starts the debugger. A couple users of the PowerShell extension have discovered that this variable will have the file path of the first opened file in the workspace. However, if they switch active files this variable does not change, meaning that the debugger will always run that first file. See more discussion here:

PowerShell/vscode-powershell@a613d5e

It would be nice if this variable got updated dynamically so that the user can run the debugger against the currently active file without having to manually edit their launch.json file each time. This is a pretty common practice when developing PowerShell scripts.