We are glad to help you learning to help yourself with simple means (well as far as possible: :)

Googling

"warning (usually harmless): 'YAML' not installed, will not store persistent state"

will show you many hits!

The second one is already an old perlmonks thread with the same question and a solution in the last post.

Please try and tell us if it helped. :)

PS: this time I'm not directly linking anymore, to encourage you practicing the search process.

(No sarcasm!!!)

see also Show Some Effort

update

and plz keep in mind that we warned you about modifying system Perl! Perlbrew would be easier.