Then I would describe the process as:

• for each line
  • if it starts with 'address', replace any space characters preceding the word 'address' with a newline
  • if not, pass the line through unchanged

So that would give me this code, which you can wrap in whatever input/output you need to do once you understand it:

while(<>){
  if(/^address/){
    s/ address/\naddress/g;
    print;
  } else {
    print;
  }
}
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