How to keep BOM from removal from Perforce unicode

I have converted entire branch with .NET and SQL sources to UTF-8 with BOM, having their Perforce file type changed to Unicode in the same operation. (Encoding difference might sound confusing, but in Perforce, Unicode file type denotes UTF-8 file content.) But later I have found out that Perforce silently elliminates BOM marker from UTF-8 files. Is it possible to set Perforce to keep UTF-8 BOM markers in files of Unicode file type? I can't find it documented.

Perforce server is switched to Unicode mode, connection encoding is UTF-8 no BOM (but changing it to UTF-8 with BOM doesn't make any difference).

Example:

check out a source file from Perforce
change file type to Unicode
convert file content to format "UTF-8 with BOM"
submit the file (now the file still keeps BOM in first 3 bytes)
remove the file from workspace
get the latest revision of the file (now the file doesn't contain BOM at the beginning)

OK, Hans Passant's comment encouraged me to re-examine P4CHARSET and finally, the answer has two parts:

For Perforce command line access, setting of P4CHARSET variable controls the behavior. To enable adding BOM to files of Unicode type, use command

p4 set P4CHARSET=utf8-bom

In order to have these files without BOM, use

p4 set P4CHARSET=utf8

For P4V The Perforce Visual Client, the setting can be changed via menu Connection > Choose Character Encoding.... Use value Unicode (UTF-8) to enable adding BOM and Unicode (UTF-8, no BOM) to suppress it.

if menu item Choose Character Encoding... is disabled, ensure the following (and then check again)
- P4V has connection to server open and working
- pane containing depot/workspace tree is focused (click inside to re-ensure this)

Notes:

if you usually combine both above ways to access Perforce, you need to apply both solutions, otherwise you will keep getting mixed results
if you want to instantly add/remove BOM to/from existing files, adjust the above settings, then remove files from workspace and add them again (see steps 5 and 6 of example posted in the question). Other server actions changing content of files (integrating, merging etc.) will do the similar
for other encoding options and their impact on BOM, see the second table in Internationalization Notes for P4D, the Perforce Server and Perforce client applications