The %fib was built but not actually used.

Well not quite, it is used for what you said:

to help looking for a fib whose initial digits are a fib too

This is what I was using it for, since I didn't feel like getting too fancy with the regex. The code I wrote was mostly just an implementation of my interpretation of the description the OP gave:

"Check 4 is fibonacci number , no , go ahaed 49 is fibonacci number , no, next 496 is fibonacci ,no, 4969 after 44693 [sic] ,after 496934 no.There isnt any fibonacci , go to next digit and do it again 9 , 96,969,9693,96934."

I wonder if any value of %fib could be an array with more than 3 elements?

Good question, I didn't try cranking up $DIGITS past 60 yet...

the task is too much unclear

Agreed, which is why I just implemented the part I (thought I) understood ;-)