Code:
alias hello {
  window -ep @hello
  drawrect -r @hello 0 1 100 100 50 50
  var %i = 1,%t = $ticks
  while (%i <= 1000) {
    drawcopy -tr @hello $rgb(255,255,255) 0 0 $window(@hello).bw $window(@hello).bh @hello 0 0
    inc %i
  }
  echo -a Using the -t switch on /drawcopy: $calc($ticks - %t)
  var %i = 1,%t = $ticks
  while (%i <= 1000) {
    drawcopy -r @hello 0 0 $window(@hello).bw $window(@hello).bh @hello 0 0
    inc %i
  }
  echo -a Not using the -t switch on /drawcopy: $calc($ticks - %t)
}

Quote:
Using the -t switch on /drawcopy: 21797
Not using the -t switch on /drawcopy: 6563


Its not exactly a bug, but using the -t switch is about 332.1195% slower.