Ruby String Encode Consecutive Letter Frequency -

i want encode string in ruby such output should in pairs decode it. want encode in such way each pair contains next distinct letter in string, , number consecutive repeats.

e.g if encode "aaabbcbbaaa" output should [["a", 3], ["b", 2], ["c", 1], ["b", 2], ["a", 3]]

here code.

def encode( s )     b = 0     e = s.length - 1     ret = []      while ( s <= e )         m = s.match( /(\w)\1*/ )         l = m[0][0]         n = m[0].length         ret << [l, n]     end     ret end 

"aaabbcbbaaa".scan(/((.)\2*)/).map{|s, c| [c, s.length]}