i use the following linux distro
Linux <system name>.home 2.6.43.5-2.fc15.i686 #1 SMP Tue May 8 12:07:12 UTC 2012 i686 i686 i386 GNU/Linux

the following is the problem

$ expr 1 + 1
2
$ expr 1 * 1
expr: syntax error
$ _

sorry if it was my mis-understanding of the manual.