"rotate -h" states:
------------------------------------------------------------------------
rotate [[-f|-flip|--flip] [horizontal | vertical]
[-r|-rotate|--rotate] [90 | 180 | 270]
[-tp|-transpose|--transpose]
[-tv|-transverse|--transverse]]
files
Options:
-------
[…]
files
The files you want to rotate. Wildcards are acceptable.
------------------------------------------------------------------------
rotate(1) states:
------------------------------------------------------------------------
SYNOPSIS
rotate { options } file [ file ... ]
------------------------------------------------------------------------
Note that in both cases, multiple files as parameter are explicitly
documented.
Nevertheless if you pass more than one file on the command line, rotate
errors out (independent of /usr/bin/csh being the real csh or the tcsh):
------------------------------------------------------------------------
→ rotate -r 90 DSCN4743.JPG DSCN4744.JPG
if: Expression Syntax.
------------------------------------------------------------------------
This happens at least on Debian 9 Stretch and Debian Sid/Bullseye as of
this writing.