pro str_replace,string1,old_substring,new_substring,reverse_search = rev n = n_elements(string1) for i=0L,n-1 do begin pos = strpos(reverse_search=rev,string1[i],old_substring) if pos lt 0 then continue string1[i] = strmid(string1[i],0,pos) + new_substring + strmid(string1[i],pos+strlen(old_substring)) endfor return end