error: can't read "result": no such variable

[Gideon Simpson]

I just started having the problem:

gideon@mymachine:~$ port list outdated
can't read "result": no such variable
    while executing
"ui_debug "sw_vers exists but running it failed: $result""
    invoked from within
"try -pass_signal {
            set macosx_version [exec /usr/bin/sw_vers -productVersion | cut 
-f1,2 -d.]
        } catch {*} {
            ui_debug "..."
    (procedure "mportinit" line 56)
    invoked from within
"mportinit ui_options global_options global_variations"
Error: /opt/local/bin/port: Failed to initialize MacPorts, can't read "result": 
no such variable

-gideon