How do I report a bug in gawkJapanese

This is described in great detail in the gawk documentation. In brief:

1. Make sure what you've discovered is really a bug by checking the documentation and, if possible, comparing with nawk and mawk.
2. Cut down the program and data to as small as possible a test case that will illustrate the bug.
3. Optionally post to comp.lang.awk; this allows others to confirm or deny the behavior, and its incorrectness (or lack thereof).
4. Send mail to <mailto:bug-gawk@gnu.org>. This automatically sends a copy to Arnold Robbins. Do not JUST post in comp.lang.awk; Arnold's readership there is sporadic, and of course any Usenet article can be missed, killed, or dropped.