"undefined subroutine &main::doubler called at t/Integer-Doubler.t line 16"
"#Looks like your test exited with 255 just after 1"
Test returned status 255 (wstat 65280, 0xff00)
	after all the subtests completed successfully
Failed Test         Stat Wstat Total Fail  List of Failed
-------------------------------------------------------------------------------
t/Integer-Doubler.t  255 65280     1    0  ??
Failed 1/1 test scripts. 0/1 subtests failed.
Files=1, Tests=1,  0 wallclock secs ( 0.00 cusr +  0.00 csys =  0.00 CPU)