I usually find hidden subfolders in working directories, which, as I suppose, were produced by the Perl 6 compiler, e.g.:
.precomp/0717742595706FA8D59800F9F9F7074236546DE7.1505852292.23535/0B/0BDF8C54D33921FEA066491D8D13C96A7CB144B9.repo-id
So, I have two questions:
Is it normal?
Is it indispensable for the compiler or there is a way to avoid it?
The .precomp folder houses the precompiled form of Perl 6 modules.
The first time you use a module it gets compiled and stored in .precomp so that it doesn't have to be compiled it again. (currently only modules, not programs)
You can delete the directory and your code will continue to function. It will just be slower. Note that it will be recreated again the next time you use a module unless the directory can't be written to. I occasionally delete it myself; though that is because I regularly rebuild Rakudo from git. I do that just to clean the remnants of older installs.
The reason for the long seemingly arbitrary directory names are due to the fact that multiple versions from multiple authors of a module may be installed at once, and the possibility of Unicode module names. There has been talk of using another system which would give the files/directories more reasonable names, it just hasn't happened yet.