///<summary>
 ///Try get a new <see cref="IEnvVarFilePath"/> object from this string.
 ///</summary>
 ///<returns><i>true</i> if <paramref name="pathString"/> is a valid file path prefixed with an environment variable and as a consequence, the returned <paramref name="envVarFilePath"/> is not null.</returns>
 ///<remarks>
 ///The path represented by this string doesn't need to exist for this operation to complete properly.
 ///The environment variable prefixing the path doesn't need to exist for this operation to complete properly.
 ///</remarks>
 ///<param name="pathString">Represents the path.</param>
 ///<param name="envVarFilePath">If this method returns <i>true</i>, this is the returned path object.</param>
 public static bool TryGetEnvVarFilePath(this string pathString, out IEnvVarFilePath envVarFilePath) {
    string failureReasonUnused;
    return pathString.TryGetEnvVarFilePath(out envVarFilePath, out failureReasonUnused);
 }
 ///<summary>
 ///Try get a new <see cref="IEnvVarFilePath"/> object from this string.
 ///</summary>
 ///<returns><i>true</i> if <paramref name="pathString"/> is a valid file path prefixed with an environment variable and as a consequence, the returned <paramref name="envVarFilePath"/> is not null.</returns>
 ///<remarks>
 ///The path represented by this string doesn't need to exist for this operation to complete properly.
 ///The environment variable prefixing the path doesn't need to exist for this operation to complete properly.
 ///</remarks>
 ///<param name="pathString">Represents the path.</param>
 ///<param name="envVarFilePath">If this method returns <i>true</i>, this is the returned path object.</param>
 ///<param name="failureReason">If this method returns <i>false</i>, this is the plain english description of the failure.</param>
 public static bool TryGetEnvVarFilePath(this string pathString, out IEnvVarFilePath envVarFilePath, out string failureReason) {
    envVarFilePath = null;
    if (pathString.IsPathStringNullOrEmpty(out failureReason)) { return false; }
    if (!pathString.IsValidEnvVarFilePath(out failureReason)) { return false; }
    envVarFilePath = new EnvVarFilePath(pathString);
    return true;
 }