5eebb559_nd_for_the_PostScript_language__Purpose
[Key] SourceFile [Purpose] 
File object from which \markup reads input. If this entry is not initially present, \markup defines it with the file object obtained from currentfile. This value is freshly fetched from the dictionary after any embedded token has been handled, so embedded PostScript tokens may change it.
Markup: a minimalist markup frontend for the PostScript language
Purpose