# \2 the second group,and so on.
# Outside the pattern,the special variables $1, $2, and so on, serve the samepurpose.
"12:50am" =~ /(\d\d):(\d\d)(..)/ # 0
"Hour is #$1, minute #$2" # "Hour is 12, minute 50"
"12:50am" =~ /((\d\d):(\d\d))(..)/ # 0
"Time is #$1" # "Time is 12:50"
"Hour is #$2, minute #$3" # "Hour is 12, minute 50"
"AM/PM is #$4" # "AM/PM is am"