Code:
alias bench1 { 
  var %i = 10000, %ticks = $ticks
  while (%i) {
    if ($left(/hello,1) == /) { noop }
    dec %i
  }
  return $calc($ticks - %ticks)
}
alias bench2 { 
  var %i = 10000, %ticks = $ticks
  while (%i) {
    if (/* iswm /hello) { noop }
    dec %i
  }
  return $calc($ticks - %ticks)
}
alias bench { 
  var %i = 10
  while (%i) {
    echo -a $!left: $bench1 ~ iswm: $bench2 
    dec %i
  }
}


Type /bench

My results:

Quote:
$left: 422 ~ iswm: 391
$left: 422 ~ iswm: 375
$left: 437 ~ iswm: 360
$left: 422 ~ iswm: 375
$left: 422 ~ iswm: 375
$left: 422 ~ iswm: 375
$left: 421 ~ iswm: 375
$left: 438 ~ iswm: 359
$left: 438 ~ iswm: 359
$left: 422 ~ iswm: 359


It seems that parsing identifiers is a slow process.