out of the box tcp-int.tcl failed

[asiboro@yen.cse.kyutech.ac.jp (Arnold P. Siboro)]

I am a new user of ns. I tried to execute an unmodified version of
tcp-int.tcl that came with ns-2, but it failed with the following
error message. Could anybody give a hint of what's wrong?
Thanks a lot.

variable "class" already exists
    (_o76 instvar line 1)
    invoked from within
"$self instvar -parse-part1 $var"
    (procedure "_o76" line 3)
    (SplitObject set line 3)
    invoked from within
"$udp1 set class 1"
    (file "tcp-int.tcl" line 45)
[arnold@shekel tcp-int]$ ns tcp-int.tcl > del
variable "class" already exists
    (_o76 instvar line 1)
    invoked from within
"$self instvar -parse-part1 $var"
    (procedure "_o76" line 3)
    (SplitObject set line 3)
    invoked from within
"$udp1 set class 1"
    (file "tcp-int.tcl" line 45)


Arnold Pandapotan SIBORO  
シボロ・アーノルド
-------------------------------------------------------------
Information Network Lab, KIT, Iizuka-shi, Japan.
九州工業大学電子情報工学科尾家研究室　

asiboro@yen.cse.kyutech.ac.jp, aps@fsai.kyutech.ac.jp
http://www.fsai.kyutech.ac.jp/‾asiboro

"That knowledge which is termed science should be acquired, 
while the seeker daily acknowleges that the fear of God
is the beginning of wisdom." (MM, p.66)