When a function's name ends with an 'x' it strips leading and trailing blanks. For example, cat('a',' b ') = 'a b ', while catx('a',' b ') = 'ab'. Similarly, call symput("var", " MWSUG ") puts " MWSUG " into macro variable var, while call symputx("var", " MWSUG ") strips the leading and trailing blanks, putting "MWSUG" into macro variable var. The 'x' functions did not become available until version 9. The older way to strip the blanks was to nest the input parameters in a strip() function, so something like cat('a', strip(' b ')) would be equivalent to catx('a', ' b ').
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