This variable retrieves the raw CLR (Common Language Runtime, Microsoft's .Net implementation) version number for .Net 4.x, if any, of the Client profile (only). If present, this is the full version number of the .Net 4.x Client installation on the target system, for example 4.0.04506.30.
You can refer to this variable as <RegCLR4ClientVersion>. Do not change its value; it has been carefully configured for cross-platform compatibility and is used internally by the installer. You can use this version number with runtime functions such as $vercmp to test for specific .Net 4.x versions. Alternatively, you can use the MsiNetAssemblySupport or VersionCLR variables.
You can compare version numbers directly using the standard relational operators < <= > >= = and <>, so a conditional expression like RegCLR4ClientVersion > 4.0 will do a proper version comparison, obviating the need for the $vercmp function.