.

base/regex.jl

@@ -208,6 +208,15 @@ end
 search(s::AbstractString, r::Regex, idx::Integer) =
     throw(ArgumentError("regex search is only available for bytestrings; use bytestring(s) to convert"))
 search(s::AbstractString, r::Regex) = search(s,r,start(s))
+_search(s::AbstractString, r::Regex, idx::Integer) = match(r, s, idx)
+
+first(m::RegexMatch) = m.offset
+last(m::RegexMatch) = m.offset + length(m.match) - 1
+
+function _replace(io, repl::AbstractString, str, m::RegexMatch)
+    write(io, "repl")
+    write(io, repl)
+end
 
 immutable RegexMatchIterator
     regex::Regex

base/string.jl

@@ -1327,8 +1327,11 @@ function _rsplit{T<:AbstractString,U<:Array}(str::T, splitter, limit::Integer, k
 end
 #rsplit(str::AbstractString) = rsplit(str, _default_delims, 0, false)
 
-_replacement(repl, str, j, k) = repl
-_replacement(repl::Function, str, j, k) = repl(SubString(str, j, k))
+_replace(io, repl, str, r) = write(io, repl)
+_replace(io, repl::Function, str, r) =
+    write(io, repl(SubString(str, first(r), last(r))))
+_search(str, pattern, offset) = search(str, pattern, offset)
+
 
 function replace(str::ByteString, pattern, repl, limit::Integer)
     n = 1
@@ -1340,7 +1343,7 @@ function replace(str::ByteString, pattern, repl, limit::Integer)
     while j != 0
         if i == a || i <= k
             write_sub(out, str.data, i, j-i)
-            write(out, _replacement(repl, str, j, k))
+            _replace(out, repl, str, r)
         end
         if k<j
             i = j
@@ -1351,7 +1354,8 @@ function replace(str::ByteString, pattern, repl, limit::Integer)
         if j > e
             break
         end
-        r = search(str,pattern,k)
+        r = _search(str,pattern,k)
+        r == nothing && break
         j, k = first(r), last(r)
         n == limit && break
         n += 1