Do iRules not support the -format switch of the TCL [clock scan] command?

Hi. I'm wondering if anyone has run into this before. I'm attempting to write a time based iRule, which I know others here have done. I am trying to scan in a date from Active Directory that I got with an LDAP query (for simplicity in the example below, I just copied/pasted it into a variable so you can see the exact format).

According to the TCL manual page, the [clock scan] command has a -format switch that can be used to help TCL parse the format of the date being input. Here is an example from the clock scan manual page:

set s [clock scan {2004-10-30 05:00:00} \
       -format {%Y-%m-%d %H:%M:%S} \
       -timezone :America/New_York]

I am trying to do the same thing in my iRule as seen below:

 when ACCESS_POLICY_AGENT_EVENT {
if { [ACCESS::policy agent_id] eq "test_irule" } {
    set pwdLastSet "1/4/2016 9:17:05 AM Eastern Standard Time;"

    set seconds_per_day 86400
    set pwdLastSet_scanned [clock scan $pwdLastSet -format {%D %T %P %z;} -locale en_US]

    [ACCESS::session data set "session.pwdLastSet" $pwdLastSet_scanned]

}

}

Unfortunately, I keep getting an error from the BigIP saying that I have the wrong number of arguments and that "-format" isn't a supported switch. Does anyone have any ideas? Is the F5 [clock scan] command somewhat crippled?

Error:

error_string         : 01070151:3: Rule [/Common/test_irule] error: /Common/test_irule:6: error: [invalid switch: "-format"][-format]

/Common/test_irule:6: error: [wrong args][clock scan $pwdLastSet -format {%D %T %P %;} -locale en_US]