Aha! the solution is simple!
I was setting variables with plain $ A=5 command; when you use $ export B="foo" everything is fine.
That is because export makes the variable available to sub-processes:
- it creates a variable in the shell
- and exports it into the environment of the shell
- the environment is passed to sub-processes of the shell.
Plain $ A="foo" just creates variables in the shell and doesn’t do anything with the environment.
The interpreter called from the shell obtains its environment from the parent — the shell. So really the variable should be exported into the environment before.