This article explains why the TCLLIBPATH env variable is not recommended for PERC package check and what you can use instead.
The TCLLIBPATH env variable for PERC package checks is actually not supported to be read into Calibre Interactive and RVE.
It is recommended to use the CALIBRE_PERC_PKG_CHECKS env variable in your run instead of TCLLIBPATH.
If you have to use the TCLLIBPATH variable, the best practice is to set it from Calibre Interactive -> Environment -> Add and set it from the runset, not the environment.