regex - regular expression to match repeated characters? -

i'm looking perl regular expression match strings made of same letters.

it should match aa, aaa, aaaa, aaaaa , on, not aabb, abba, aaab, aaaabaa , on.

i know can use \1 refer first character /(.)\1/, match aabb. advice?

this seems work me:

/^(.)\1*$/ 

the ^ character matches beginning of string, , $ matches end.

the whole expression can translated into: "at beginning of string, match character, followed number of same character, followed end of string.