Do you plan to call os.path.expandvars?

I request to be able to fill in the environment variable name by calling os.path.environmentvars when setting the value in main.py#L98.

An environment variable name is, for example, %TEMP% (in Windows).

[.env]
LOG_DIR=%TEMP%\log

If possible, it would be nice if it could be called recursively. os.path.expandvars will only expand the environment variable name once.

def expandvarsRecursive(value):.
    expanded = os.path.expandvars(value)
    return value if expanded == value else expandvarsRecursive(expanded)

The reason for this is that if it is called recursively, we don't have to keep track of the same values.

[.env]
PROJECT_HOME=C:\project
LOG_DIR=%PROJECT_HOME%\log
TRACE_LOG_DIR=%LOG_DIR%\trace

Please consider this.

Start in src/dotenv/main.py around line 98 and trace how values from .env files are expanded. Check how Windows-style variables and recursive references should behave, then verify the LOG_DIR and TRACE_LOG_DIR examples resolve as requested. No linked tests or further maintainer guidance are provided.