so guys i am doing some Perl coding and i need a bit of help with my regular expressions.

I need one that will search a string for an instance of aaaa then set $1 to the position of the first a in the string, set $2 to the aaaa's plus the 5 most surrounding charterers if this is not possible sorry

input: ctagtactatcgcatcgatcaaaatgtttctactac
given this input $1 should be 21
and $2 should be cgatcaaaatgttt