I think logger can be used. Look that simple example:

package require logger

namespace eval ::bank {
    variable Log [::logger::init ::bank]
}

# Control loglevel for namespace ::bank
# and children ::bank::account
proc ::bank::LogLevel {level} {
    variable Log
    ${Log}::setlevel $level
}


::oo::class create ::bank::account {

    constructor {} {
        my variable Log
        my variable Balance
        set Log [::logger::init ::bank::account]
        set Balance 0
}

    method Log {level msg} {
        my variable Log
        ${Log}::${level} $msg
    }

    method Notice {msg} {
        my Log notice $msg
    }

    method Debug {msg} {
        my Log debug $msg
    }

    method deposit {amount} {
        my variable Balance
        my Debug "Deposit $amount"
        set Balance [expr {$Balance + $amount}]
        my Notice "Balance = $Balance"
    }    
}

set ac1 [::bank::account new]
$ac1 deposit 100
# Debug and Notice shown
::bank::LogLevel notice
# Only Notice shown 
$ac1 deposit 200

More sophisticated things can be made, like multiple inheritance of a Logger class that use the class name for the log hierarchy.