FPAT =  ([^,]*)|("([^"]|"")+")
------------------------------------------------

"PDQ",,,
  4:   
      <1: PDQ>
      <2: >
      <3: >
      <4: >
 
------------------------------------------------

"line 1",,,"http://file.a/A%20Guide%20"
  4:   
      <1: line 1>
      <2: >
      <3: >
      <4: http://file.a/A%20Guide%20>
 
------------------------------------------------

"line 2",,,"https://www.whitgt.pdf"
  4:   
      <1: line 2>
      <2: >
      <3: >
      <4: https://www.whitgt.pdf>
 
------------------------------------------------

"line 3, and xyz",,,"http://www.c/main.pdf"
  4:   
      <1: line 3, and xyz>
      <2: >
      <3: >
      <4: http://www.c/main.pdf>
 
------------------------------------------------

"line 4 "" and abc",,,http://file.a/A%20Guide%20
  4:   
      <1: line 4 " and abc>
      <2: >
      <3: >
      <4: http://file.a/A%20Guide%20>
 
------------------------------------------------

line 5,,,https://www.whitgt.pdf
  4:   
      <1: line 5>
      <2: >
      <3: >
      <4: https://www.whitgt.pdf>
 
------------------------------------------------

line 6,,,http://file.a/A%20Guide%20
  4:   
      <1: line 6>
      <2: >
      <3: >
      <4: http://file.a/A%20Guide%20>