% proc a {n} { for {set i 0} {$i < $n} {incr i} { if [llength $i] { continue } } } % proc b {n} { for {set i 0} {$i < $n} {incr i} { if {[llength $i]} { continue } } } % time {a 10000} 95375 microseconds per iteration % time {b 10000} 59353 microseconds per iteration