install perl before using tlmgr
the ./ seems to be the real problem
yihui updated branch pkg/knitr Mon Oct  6 01:37:39 CDT 2014
yihui updated branch pkg/knitr Mon Oct  6 13:00:30 CDT 2014
yihui updated branch pkg/knitr Tue Oct  7 11:27:40 CDT 2014
yihui updated branch pkg/knitr Wed Oct  8 19:07:52 CDT 2014