$ tktest.pl
1..1
ok 1 - Events processed
$ Xvfb :19 &
$ pid=$!
$ DISPLAY=:19 tktest.pl
1..1
not ok 1 - Events processed
#   Failed test 'Events processed'
#   at /home/choroba/tktest.pl line 27.
#          got: '0'
#     expected: '1'
# Looks like you failed 1 test of 1.
$ kill $pid