diff --git a/all.sas b/all.sas
index 1cb860a..ee58483 100644
--- a/all.sas
+++ b/all.sas
@@ -43,6 +43,60 @@ options noquotelenmax;
 %mend mf_abort;
 
 /** @endcond *//**
+  @file
+  @brief de-duplicates a macro string
+  @details Removes all duplicates from a string of words.  A delimeter can be
+  chosen.  Is inspired heavily by this excellent [macro](
+  https://github.com/scottbass/SAS/blob/master/Macro/dedup_mstring.sas) from
+  [Scott Base](https://www.linkedin.com/in/scottbass).  Case sensitive.
+
+  Usage:
+
+      %let str=One two one two and through and through;
+      %put %mf_dedup(&str);
+      %put %mf_dedup(&str,outdlm=%str(,));
+
+  Which returns:
+
+      > One two one and through
+      > One,two,one,and,through
+
+  @param [in] str String to be deduplicated
+  @param [in] indlm= ( ) Delimeter of the input string
+  @param [out] outdlm= ( ) Delimiter of the output string
+
+  <h4> Related Macros </h4>
+  @li mf_trimstr.sas
+  @li mf_wordsinstr1butnotstr2.sas
+
+  @version 9.2
+  @author Allan Bowe
+**/
+
+%macro mf_dedup(str
+  ,indlm=%str( )
+  ,outdlm=%str( )
+)/*/STORE SOURCE*/;
+
+%local num word i pos out;
+
+%* loop over each token, searching the target for that token ;
+%let num=%sysfunc(countc(%superq(str),%str(&indlm)));
+%do i=1 %to %eval(&num+1);
+  %let word=%scan(%superq(str),&i,%str(&indlm));
+  %let pos=%sysfunc(indexw(&out,&word,%str(&outdlm)));
+  %if (&pos eq 0) %then %do;
+    %if (&i gt 1) %then %let out=&out%str(&outdlm);
+    %let out=&out&word;
+  %end;
+%end;
+
+%unquote(&out)
+
+%mend mf_dedup;
+
+
+/**
   @file mf_existds.sas
   @brief Checks whether a dataset OR a view exists.
   @details Can be used in open code, eg as follows: