RE0509

metacharacters relation to match:

   *:0-multi

   +:1-multi

   ?:0-1

   {n},{n,m},{n,}:the number of matching

string switch

   eg: pattern="lynn|coco"

       src1="hello,my name is lynn"

       result1="lynn"

       src2="hello,my name is coco"

       result2="coco"

ignore case

    eg:pattern="(?i)Lynn"

    src="hello,my name is lynn"

   result="lynn"

multi-repeat-character

   eg:pattern="n{2}"

   src="hello,my name is lynn"

   result="nn"

digital match

   eg:pattern="\d+"

   src="I am 24 years old but 18 years in school"

   result="24","18"

   

   eg:pattern="[0-9]+"

   src="I am 24 years old but 18 years in school"

   result="24","18"

   

optional character match

   eg:pattern="colou?r"

   src1="color"    result=color

   src2="colour"  result=colour