diff --git a/base/mp_chop.sas b/base/mp_chop.sas
new file mode 100644
index 0000000..52dcd2b
--- /dev/null
+++ b/base/mp_chop.sas
@@ -0,0 +1,184 @@
+/**
+  @file
+  @brief Splits a file of ANY SIZE by reference to a search string.
+  @details Provide a fileref and a search string to chop off part of a file.
+
+  Works by reading in the file byte by byte, then marking the beginning and end
+  of each matched string, before finally doing the chop.
+
+  Choose whether to keep the FIRST or the LAST section of the file.  Optionally,
+  use an OFFSET to fix the precise chop point.
+
+  Usage:
+
+      %let src="%sysfunc(pathname(work))/file.txt";
+      %let str=Chop here!;
+      %let out1="%sysfunc(pathname(work))/file1.txt";
+      %let out2="%sysfunc(pathname(work))/file2.txt";
+      %let out3="%sysfunc(pathname(work))/file3.txt";
+      %let out4="%sysfunc(pathname(work))/file4.txt";
+
+      data _null_;
+        file &src;
+        put "startsection&str.endsection";
+      run;
+
+      %mp_chop(&src, matchvar=str, keep=FIRST, outfile=&out1)
+      %mp_chop(&src, matchvar=str, keep=LAST, outfile=&out2)
+      %mp_chop(&src, matchvar=str, keep=FIRST, matchpoint=END, outfile=&out3)
+      %mp_chop(&src, matchvar=str, keep=LAST, matchpoint=END, outfile=&out4)
+
+      filename results (&out1 &out2 &out3 &out4);
+      data _null_;
+        infile results;
+        input;
+        list;
+      run;
+
+  Results:
+    @li `startsection`
+    @li `Chop here!endsection`
+    @li `startsectionChop here!`
+    @li `endsection`
+
+  For more examples, see mp_chop.test.sas
+
+  @param [in] infile The QUOTED path to the file on which to perform the chop
+  @param [in] matchvar= Macro variable NAME containing the string to split by
+  @param [in] matchpoint= (START) Valid values:
+    @li START - chop at the beginning of the string in `matchvar`.
+    @li END - chop at the end of the string in `matchvar`.
+  @param [in] offset= (0) An adjustment to the precise chop location, by
+    by reference to the `matchpoint`. Should be a positive or negative integer.
+  @param [in] keep= (FIRST) Valid values:
+    @li FIRST - keep the section of the file before the chop
+    @li LAST - keep the section of the file after the chop
+  @param [in] mdebug= (0) Set to 1 to provide macro debugging
+  @param outfile= (0) Optional QUOTED path to the adjusted output file (avoids
+    overwriting the first file).
+
+  <h4> SAS Macros </h4>
+  @li mf_getuniquefileref.sas
+  @li mf_getuniquename.sas
+
+  <h4> Related Macros </h4>
+  @li mp_gsubfile.sas
+  @li mp_replace.sas
+  @li mp_chop.test.sas
+
+  @version 9.4
+  @author Allan Bowe
+
+**/
+
+%macro mp_chop(infile,
+  matchvar=,
+  matchpoint=START,
+  keep=FIRST,
+  offset=0,
+  mdebug=0,
+  outfile=0
+)/*/STORE SOURCE*/;
+
+%local fref0 dttm ds1 outref;
+%let fref0=%mf_getuniquefileref();
+%let ds1=%mf_getuniquename(prefix=allchars);
+%let ds2=%mf_getuniquename(prefix=startmark);
+
+%if &outfile=0 %then %let outfile=&infile;
+
+/* START */
+%let dttm=%sysfunc(datetime());
+
+filename &fref0 &infile lrecl=1 recfm=n;
+
+/* create dataset with one char per row */
+data &ds1;
+  infile &fref0;
+  input sourcechar $char1. @@;
+  format sourcechar hex2.;
+run;
+
+/* get start & stop position of first matchvar string (one row, two vars) */
+data &ds2;
+  /* set find string to length in bytes to cover trailing spaces */
+  length string $ %length(%superq(&matchvar));
+  string =symget("&matchvar");
+  drop string;
+
+  firstchar=char(string,1);
+  findlen=lengthm(string); /* <- for trailing bytes */
+
+  do _N_=1 to nobs;
+    set &ds1 nobs=nobs point=_N_;
+    if sourcechar=firstchar then do;
+      pos=1;
+      s=0;
+      do point=_N_ to min(_N_ + findlen -1,nobs);
+        set &ds1 point=point;
+        if sourcechar=char(string, pos) then s + 1;
+        else goto _leave_;
+        pos+1;
+      end;
+      _leave_:
+      if s=findlen then do;
+        START =_N_;
+        _N_ =_N_+ s - 1;
+        STOP =_N_;
+        output;
+        /* matched! */
+        stop;
+      end;
+    end;
+  end;
+  stop;
+  keep START STOP;
+run;
+
+%local split;
+%let split=0;
+data _null_;
+  set &ds2;
+  if "&matchpoint"='START' then do;
+    if "&keep"='FIRST' then mp=start;
+    else if "&keep"='LAST' then mp=start-1;
+  end;
+  else if "&matchpoint"='END' then do;
+    if "&keep"='FIRST' then mp=stop+1;
+    else if "&keep"='LAST' then mp=stop;
+  end;
+  split=mp+&offset;
+  call symputx('split',split);
+run;
+%if &split=0 %then %do;
+  %put &sysmacroname: No match found in &inref for string %superq(matchvar);
+  %return;
+%end;
+
+data _null_;
+  file &outfile recfm=n;
+  set &ds1;
+%if &keep=FIRST %then %do;
+  if _n_ ge &split then stop;
+%end;
+%else %do;
+  if _n_ gt &split;
+%end;
+  put sourcechar char1.;
+run;
+
+%if &mdebug=0 %then %do;
+  filename &fref0 clear;
+%end;
+%else %do;
+  data _null_;
+    infile &infile lrecl=32767;
+    input;
+    list;
+    if _n_>50 then stop;
+  run;
+%end;
+/* END */
+%put &sysmacroname took %sysevalf(%sysfunc(datetime())-&dttm) seconds to run;
+
+%mend mp_chop;
diff --git a/base/mp_replace.sas b/base/mp_replace.sas
index a989e9e..32ea3d4 100644
--- a/base/mp_replace.sas
+++ b/base/mp_replace.sas
@@ -35,7 +35,7 @@
   @param infile The QUOTED path to the file on which to perform the substitution
   @param findvar= Macro variable NAME containing the string to search for
   @param replacevar= Macro variable NAME containing the replacement string
-  @param outfile= (0) Optional QUOTED path to an the adjusted output file (to
+  @param outfile= (0) Optional QUOTED path to the adjusted output file (to
     avoid overwriting the first file).
 
   <h4> SAS Macros </h4>
@@ -43,7 +43,9 @@
   @li mf_getuniquename.sas
 
   <h4> Related Macros </h4>
-  @li mp_gsubfile.test.sas
+  @li mp_chop.sas
+  @li mp_gsubfile.sas
+  @li mp_replace.test.sas
 
   @version 9.4
   @author Bartosz Jabłoński