anchor.diff:  These default values can then be overridden at runtime with a different file located in one of the custom locations.
   
   NOTE: If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, `SPRING_CONFIG_NAME` instead of `spring.config.name`).
  +See <<boot-features-external-config-relaxed-binding-from-environment-variables>> for details.
   
   NOTE: If your application runs in a container, then JNDI properties (in `java:comp/env`) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.
   
  
positive.code: | Standard YAML list syntax or comma-separated values
  
  | Environment Variables
  | Upper case format with underscore as the delimiter.
    `_` should not be used within a property name
  | Numeric values surrounded by underscores, such as `MY_ACME_1_OTHER = my.acme[1].other`
  
  | System properties
  | Camel case, kebab case, or underscore notation
  
negative.code: The properties above will bind to a `Map` with `/key1`, `/key2` and `key3` as the keys in the map.
  
  NOTE: For YAML files, the brackets need to be surrounded by quotes for the keys to be parsed properly.
  
  
  [[boot-features-external-config-relaxed-binding-from-environment-variables]]
  ===== Binding from Environment Variables
  Most operating systems impose strict rules around the names that can be used for environment variables.
  For example, Linux shell variables can contain only letters (`a` to `z` or `A` to `Z`), numbers (`0` to `9`) or the underscore character (`_`).
  By convention, Unix shell variables will also have their names in UPPERCASE.
  
  Spring Boot's relaxed binding rules are, as much as possible, designed to be compatible with these naming restrictions.
  
  To convert a property name in the canonical-form to an environment variable name you can follow these rules:
  
  * Replace dots (`.`) with underscores (`_`).
  * Remove any dashes (`-`).
  * Convert to uppercase.
  
  For example, the configuration property `spring.main.log-startup-info` would be an environment variable named `SPRING_MAIN_LOGSTARTUPINFO`.
  
  NOTE: Underscores cannot be used to replace the dashes in property names.
  If you attempt to use `SPRING_MAIN_LOG_STARTUP_INFO` with the example above, no value will be bound.
  
  Environment variables can also be used when binding to object lists.
  To bind to a `List`, the element number should be surrounded with underscores in the variable name.
  
  For example, the configuration property `my.acme[0].other` would use an environment variable named `MY_ACME_0_OTHER`.
  
  
  
  [[boot-features-external-config-complex-type-merge]]
  