Function prefix

static/editor.md/lib/codemirror/mode/perl/perl.js:809–816

(stream, c)

// return a part of prefix of current stream from current position
function prefix(stream, c){
  if(c){
    var x=stream.pos-c;
    return stream.string.substr((x>=0?x:0),c);}
  else{
    return stream.string.substr(0,stream.pos-1);
  }
}

// return a part of suffix of current stream from current position
function suffix(stream, c){