search for the first case-sensitive match by default, raising an
\exception{ImportError} if no such file is found, so \code{import file}
will not import a module named \samp{FILE.PY}. Case-insensitive
-matching can be requested by setting the PYTHONCASEOK environment
+matching can be requested by setting the \envvar{PYTHONCASEOK} environment
variable before starting the Python interpreter.
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