a function that takes code and returns a list of variable names needing declaration

getVars.js

var getVars = function( dummy, err, re ) {
  try { eval( dummy ) } catch( e ) { err += e }
  
  re = new RegExp( "^" + err.replace( dummy, "(\\w+)" ) + "$" )
  
  return function( code ) {
    var args = []
      , name
    
    while ( 1 ) {
      try { Function.apply( Function, args.concat( code ) )() }
      
      catch( e ) {
        name = ( re.exec( e ) || [] )[ 1 ]

        if ( !name ) throw e
        
        args.push( name )
        continue
      }
      return args      
    }
  }
}( "_" + Date.now(), "" )