I dont know coding in Perl. I will just tell you an algorithm that strikes me. I expect that Perl has some delimiter for a string like C++ has '\0'. I will refer to the delimiter character to as delimiter The algorithm is simple,

Start from the end character and traverse till first.
Begin loop
if character index= first then
print string(current index)
else if character = ' ' then /*space*/
print string(current index)
print space
set character = delimiter /* Here I am cutting the string. You can cal
+l some garbage collecting function to free up the rest of the memory 
+space*/
end if
End loop

/* This algorithm will just print the string in reverse worded way. Bu
+t in case you need a reversed string you can go on appending whatever
+ is printed here to the result string*/
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Originally posted as a Categorized Answer.