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<script>
    
    $(document).ready( function() {
      
      //function that pulls param value by name
  		function getParameterByName(name, url) {
    		if (!url) url = window.location.href;
    		name = name.replace(/[\[\]]/g, "\\$&");
    		var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
        		results = regex.exec(url);
    		if (!results) return null;
    		if (!results[2]) return '';
    		return decodeURIComponent(results[2].replace(/\+/g, " "));
		}
        
        //store value in a variable
        var paramValue = getParameterByName('source');
        
        //check to see if variable has correct value
        console.log(getParameterByName('source'));
      
// Case 1

      if(paramValue == "facebook") {
      ijQuery( 'form' ).find( 'input[name="redirect"]' ).val('https://www.facebook.com');
      
// Case 2

      } else if(paramValue == "instapage") {
      ijQuery( 'form' ).find( 'input[name="redirect"]' ).val('https://www.instapage.com');
      }

//ready

    });
</script>