+= adds the value of the right parameter to the value of the left parameter and sets the left parameter to the resulting value. The left parameter should be a variable that contains a string, decimal, or integer value.

This symbol performs mathematical addition if both parameters contain decimal or integer values. The result will be a decimal if either parameter is a decimal value.

This symbol performs string concatenation if either parameter is a string. The result is the left parameter followed by the right parameter.

Note: If the parameter on the right hand side of the symbol is a negative literal it should be surrounded by parentheses. For example, ($var += (-1)).

[(Variable: 'Left_Parameter') += Right_Parameter]

<?LassoScript
  (Variable: 'Left_Parameter') += Right_Parameter;
?>

<?LassoScript
  $Left_Parameter += Right_Parameter;
?>