[perl mode] Allow underscore separators in numbers

Closes codemirror#6866

Author: marijnh

mode/perl/perl.js

@@ -513,9 +513,8 @@ CodeMirror.defineMode("perl",function(){
  return null;
  if(state.chain)
  return tokenChain(stream,state,state.chain,state.style,state.tail);
- if(stream.match(/^\-?[\d\.]/,false))
- if(stream.match(/^(\-?(\d*\.\d+(e[+-]?\d+)?|\d+\.\d*)|0x[\da-fA-F]+|0b[01]+|\d+(e[+-]?\d+)?)/))
- return 'number';
+ if(stream.match(/^(\-?((\d[\d_]*)?\.\d+(e[+-]?\d+)?|\d+\.\d*)|0x[\da-fA-F_]+|0b[01_]+|\d[\d_]*(e[+-]?\d+)?)/))
+ return 'number';
  if(stream.match(/^<<(?=[_a-zA-Z])/)){ // NOTE: <<SOMETHING\n...\nSOMETHING\n
  stream.eatWhile(/\w/);
  return tokenSOMETHING(stream,state,stream.current().substr(2));}