Expect: How to get the exit code from spawned process

spawn true
expect eof
catch wait result
exit [lindex $result 3]

spawn false
expect eof
catch wait result
exit [lindex $result 3]

 [Linux Dev:anr ]$ cat testexit.sh
 #!/bin/bash
 export tmp_script_file="/home/anr/tmp_script_temp.sh"
 cp /home/anr/tmp_script $tmp_script_file
 chmod a+x $tmp_script_file
 cat $tmp_script_file
 expect << 'EOF'
 set timeout -1
 spawn  $env(tmp_script_file)
 expect {
 "INVALID "  { exit 4 }
 timeout     { exit 4 }
 eof
 }

 foreach {pid spawnid os_error_flag value} [wait] break

 if {$os_error_flag == 0} {
     puts "exit status: $value"
     exit $value
 } else {
     puts "errno: $value"
     exit $value
 }
 EOF
 echo "spawned process status" $?
 rm -f $tmp_script_file
 echo "done"

 [Linux Dev:anr ]$ cat tmp_script
 exit 3

 [Linux Dev:anr ]$ ./testexit.sh
 exit 3
 spawn /home/anr/tmp_script_temp.sh
 exit status: 3
 spawned process status 3
 done

set program [lindex $argv 0]
set arguments [lrange $argv 1 end]
spawn $program {*}$arguments

spawn [lindex $argv 0] [lrange $argv 1 end]

spawn [lindex $argv 0] {*}[lrange $argv 1 end]

proc lshift {varname} {      
    upvar 1 $varname var
    set var [lassign $var first]
    return $first
}

expect1.6> set argv {foo bar baz}
foo bar baz
expect1.7> set script [lshift argv]
foo
expect1.8> set script
foo
expect1.9> set argv
bar baz