In looking for Asymptote files, asy will search the
following paths, in the order listed:
dir or environment variable ASYMPTOTE_DIR
(separated by : under UNIX and
; under MSDOS);
ASYMPTOTE_HOME; if this variable is not set,
the directory .asy in the user’s home directory
(%USERPROFILE%\.asy under MSDOS) is used;
Asymptote system directory (by default,
/usr/local/share/asymptote under UNIX and
C:\Program Files\Asymptote under MSDOS).
Asymptote examples directory (by default,
/usr/local/share/doc/asymptote/examples under UNIX and
C:\Program Files\Asymptote\examples under MSDOS).