Temporary named pipes in Hpux Kornshell

Tried the following on Hpux 11.11, using both ksh, and dtksh

$diff <(sort file1) <(sort file2)

$ ksh: syntax error: `(' unexpected

Strange thing is I tried the same command under RHEL5 using ksh 93 and it works fine. Does anyone know if this is possible on HPUX without the use of temporary files ?

Thanks