Error about uniaxialMaterial Hardening

[bridger]

The code is as follows:
wipe
set b 0.1; set d 0.5
set E 2.0e8; set fy 4.1e5
uniaxialMaterial Hardening 4 $E $fy 0. [expr 0.02/(1-0.02)*$E]
(OpenSees version 2.3.1)

But the error occurs,
invalid command name "uniaxialMaterial"
while executing
"uniaxialMaterial Hardening 4 $E $fy 0. [expr 0.02/(1-0.02)*$E]"
(file "cantilever.tcl" line 4)

Who can help me? Thanks!

[vesna]

Can you try to use the latest version of OpenSees?