Package tracerx implements a simple tracer function that uses environment variables to control the output. It is a generalized package inspired by git's GIT_TRACE mechanism. By default, tracerx will look for the TRACERX_TRACE environment variable. The default can by changed by setting the DefaultKey. The values control where the tracing is output as follows: By default, messages will be prefixed with "trace: ". This prefix can be modified by setting Prefix. Each key can have an associated performance key, e.g. TRACERX_TRACE_PERFORMANCE. If this key is 1 or "true" performance output will be written to the same output as the tracing output.