Logging into the journald is just pipeing your echoed message to systemd-cat

If one wants to calculate in vim one simply has to write the following line:

2 pi mult

and visually select it with V then pass it to rpnl or calc or bc or so via xargs

:!xargs rpnl

to get the result in the line.

This trick also works …

Ctrl+[; Space; Enter; Ctrl+]