How is EMPERL_PRELOAD_FILE or PRELOAD_FILE used?

[vadimkantorov]

I'm trying to understand what files/directories get bundled with the WASM module, but I can't find how/where this variables from https://github.com/haukex/webperl/blob/master/build/emperl_config.sh get used

[haukex]

Note WebPerl currently consists of two repositories, this one plus the patched Perl5 source. EMPERL_PRELOAD_FILE is used for emcc's --preload-file option, see https://github.com/haukex/emperl5/blob/327812bab/Makefile.SH#L1097