The manual at
http://www.conitec.net/wdlman4.pdf lists two definitions for string1 and string 2.
string1, string2
String synonyms for use in actions (eg. to display a text if the mouse touches the object).
string = string1, string2...;
The actual text, containing of one or more strings (define maximum number in strings
beforehand!). String may be changed by functions during gameplay. If a string name null is
assigned, no text is displayed. If the text contains more than one string, individual strings can
be accessed through a [] index suffix, e.g.
my_text.string[7] = new_string;
Hope that helps!