[~] $ perl -Mre=debug -e'qr/\d{2}/'
Freeing REx: `,'
Compiling REx `\d{2}'
size 4 first at 3
   1: CURLY {2,2}(4)
   3:   DIGIT(0)
   4: END(0)
stclass `DIGIT' minlen 2 
Freeing REx: `\d{2}'
[~] $ perl -Mre=debug -e'qr/\d\d/'
Freeing REx: `,'
Compiling REx `\d\d'
size 3 first at 1
   1: DIGIT(2)
   2: DIGIT(3)
   3: END(0)
stclass `DIGIT' minlen 2 
Freeing REx: `\d\d'