not according to perldoc:

perldoc IPC::Open3

snippage here. . . .

DESCRIPTION
     Extremely similar to open2(), open3() spawns the given $cmd
     and connects RDRFH for reading, WTRFH for writing, and ERRFH
     for errors.  If ERRFH is '', or the same as RDRFH, then
     STDOUT and STDERR of the child are on the same file handle.
     The WTRFH will have autoflush turned on.

     If WTRFH begins with "<&", then WTRFH will be closed in the
     parent, and the child will read from it directly.  If RDRFH
     or ERRFH begins with ">&", then the child will send output
     directly to that file handle.  In both cases, there will be
     a dup(2) instead of a pipe(2) made.
[download]

the open3 STDOUT and STDERR can be on the same filehandle.