diff --git a/base/deprecated.jl b/base/deprecated.jl
index 11751f36ad6fb..e82234ff83d6c 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -1344,14 +1344,19 @@ end
 function replace(s::AbstractString, pat, f, n::Integer)
     if n <= 0
         depwarn(string("`replace(s, pat, r, count)` with `count <= 0` is deprecated, use ",
-                       "`replace(s, pat, r, typemax(Int))` or `replace(s, pat, r)` instead"),
+                       "`replace(s, pat=>r, count=typemax(Int))` or `replace(s, pat=>r)` instead"),
                 :replace)
-        replace(s, pat, f)
+        replace(s, pat=>f)
     else
-        replace_new(String(s), pat, f, n)
+        depwarn(string("`replace(s, pat, r, count)` is deprecated, use ",
+                       "`replace(s, pat=>r, count=count)`"),
+                :replace)
+        replace(String(s), pat=>f, count=n)
     end
 end
 
+@deprecate replace(s::AbstractString, pat, f) replace(s, pat=>f)
+
 # PR #22475
 @deprecate ntuple(f, ::Type{Val{N}}) where {N}  ntuple(f, Val(N))
 @deprecate fill_to_length(t, val, ::Type{Val{N}}) where {N} fill_to_length(t, val, Val(N)) false
diff --git a/base/libgit2/utils.jl b/base/libgit2/utils.jl
index 1eacbd5e7d180..5d6568336b5dd 100644
--- a/base/libgit2/utils.jl
+++ b/base/libgit2/utils.jl
@@ -83,7 +83,7 @@ Standardise the path string `path` to use POSIX separators.
 """
 function posixpath end
 if Sys.iswindows()
-    posixpath(path) = replace(path,'\\','/')
+    posixpath(path) = replace(path,'\\' => '/')
 elseif Sys.isunix()
     posixpath(path) = path
 end
diff --git a/base/markdown/GitHub/table.jl b/base/markdown/GitHub/table.jl
index 3b10945e37ae1..b449da258bfd3 100644
--- a/base/markdown/GitHub/table.jl
+++ b/base/markdown/GitHub/table.jl
@@ -11,7 +11,7 @@ function parserow(stream::IO)
         row = split(line, r"(?<!\\)\|")
         length(row) == 1 && return
         isempty(row[1]) && shift!(row)
-        map!(x -> strip(replace(x, "\\|", "|")), row, row)
+        map!(x -> strip(replace(x, "\\|" => "|")), row, row)
         isempty(row[end]) && pop!(row)
         return row
     end
@@ -104,7 +104,7 @@ _dash(width, align) =
 
 function plain(io::IO, md::Table)
     cells = mapmap(md.rows) do each
-        replace(plaininline(each), "|", "\\|")
+        replace(plaininline(each), "|" => "\\|")
     end
     padcells!(cells, md.align, len = length, min = 3)
     for i = axes(cells,1)
diff --git a/base/markdown/render/html.jl b/base/markdown/render/html.jl
index 2c350c666680d..a48180509400f 100644
--- a/base/markdown/render/html.jl
+++ b/base/markdown/render/html.jl
@@ -31,7 +31,7 @@ for ch in "'`!\$%()=+{}[]"
 end
 
 function htmlesc(io::IO, s::AbstractString)
-    # s1 = replace(s, r"&(?!(\w+|\#\d+);)", "&amp;")
+    # s1 = replace(s, r"&(?!(\w+|\#\d+);)" => "&amp;")
     for ch in s
         print(io, get(_htmlescape_chars, ch, ch))
     end
diff --git a/base/markdown/render/rst.jl b/base/markdown/render/rst.jl
index 377aee7399926..d4bbaf199a9b5 100644
--- a/base/markdown/render/rst.jl
+++ b/base/markdown/render/rst.jl
@@ -124,7 +124,7 @@ end
 
 rstinline(io::IO, f::Footnote) = print(io, "[", f.id, "]_")
 
-rstescape(s) = replace(s, "\\", "\\\\")
+rstescape(s) = replace(s, "\\" => "\\\\")
 
 rstinline(io::IO, s::AbstractString) = print(io, rstescape(s))
 
diff --git a/base/markdown/render/terminal/formatting.jl b/base/markdown/render/terminal/formatting.jl
index 36a4d390a7138..5055b80e11c12 100644
--- a/base/markdown/render/terminal/formatting.jl
+++ b/base/markdown/render/terminal/formatting.jl
@@ -51,7 +51,7 @@ end
 # Wrapping
 
 function ansi_length(s)
-    replace(s, r"\e\[[0-9]+m", "") |> length
+    replace(s, r"\e\[[0-9]+m" => "") |> length
 end
 
 words(s) = split(s, " ")
diff --git a/base/markdown/render/terminal/render.jl b/base/markdown/render/terminal/render.jl
index c8ba9455a0ec9..5f6fd32923fcd 100644
--- a/base/markdown/render/terminal/render.jl
+++ b/base/markdown/render/terminal/render.jl
@@ -114,7 +114,7 @@ function terminline(io::IO, content::Vector)
 end
 
 function terminline(io::IO, md::AbstractString)
-    print(io, replace(md, r"[\s\t\n]+", " "))
+    print(io, replace(md, r"[\s\t\n]+" => " "))
 end
 
 function terminline(io::IO, md::Bold)
diff --git a/base/methodshow.jl b/base/methodshow.jl
index 35bae1f1671a0..1430b86ef1d4b 100644
--- a/base/methodshow.jl
+++ b/base/methodshow.jl
@@ -203,7 +203,7 @@ function url(m::Method)
     file = string(m.file)
     line = m.line
     line <= 0 || ismatch(r"In\[[0-9]+\]", file) && return ""
-    Sys.iswindows() && (file = replace(file, '\\', '/'))
+    Sys.iswindows() && (file = replace(file, '\\' => '/'))
     if inbase(M)
         if isempty(Base.GIT_VERSION_INFO.commit)
             # this url will only work if we're on a tagged release
diff --git a/base/pkg/reqs.jl b/base/pkg/reqs.jl
index b84ce5614993d..b02c2aaa9231a 100644
--- a/base/pkg/reqs.jl
+++ b/base/pkg/reqs.jl
@@ -19,7 +19,7 @@ struct Requirement <: Line
     system::Vector{AbstractString}
 
     function Requirement(content::AbstractString)
-        fields = split(replace(content, r"#.*$", ""))
+        fields = split(replace(content, r"#.*$" => ""))
         system = AbstractString[]
         while !isempty(fields) && fields[1][1] == '@'
             push!(system,shift!(fields)[2:end])
diff --git a/base/process.jl b/base/process.jl
index 2534b6d2e923d..3294f8a22ced2 100644
--- a/base/process.jl
+++ b/base/process.jl
@@ -107,7 +107,7 @@ function show(io::IO, cmd::Cmd)
             with_output_color(:underline, io) do io
                 print_shell_word(io, arg, shell_special)
             end
-        end, '`', "\\`")
+        end, '`' => "\\`")
     end, ' '))
     print(io, '`')
     print_env && (print(io, ","); show(io, cmd.env))
diff --git a/base/repl/LineEdit.jl b/base/repl/LineEdit.jl
index e0b443634dbe5..19c75910c3ef6 100644
--- a/base/repl/LineEdit.jl
+++ b/base/repl/LineEdit.jl
@@ -1883,12 +1883,12 @@ function bracketed_paste(s; tabwidth=options(s).tabwidth)
     ps = state(s, mode(s))
     str = readuntil(ps.terminal, "\e[201~")
     input = str[1:prevind(str, end-5)]
-    input = replace(input, '\r', '\n')
+    input = replace(input, '\r' => '\n')
     if position(buffer(s)) == 0
         indent = Base.indentation(input; tabwidth=tabwidth)[1]
         input = Base.unindent(input, indent; tabwidth=tabwidth)
     end
-    return replace(input, '\t', " "^tabwidth)
+    return replace(input, '\t' => " "^tabwidth)
 end
 
 function tab_should_complete(s)
diff --git a/base/repl/REPL.jl b/base/repl/REPL.jl
index a3175eb35d901..838c45e95f24b 100644
--- a/base/repl/REPL.jl
+++ b/base/repl/REPL.jl
@@ -450,7 +450,7 @@ function add_history(hist::REPLHistoryProvider, s)
     entry = """
     # time: $(Libc.strftime("%Y-%m-%d %H:%M:%S %Z", time()))
     # mode: $mode
-    $(replace(str, r"^"ms, "\t"))
+    $(replace(str, r"^"ms => "\t"))
     """
     # TODO: write-lock history file
     seekend(hist.history_file)
@@ -946,7 +946,7 @@ function setup_interface(
                         tail = lstrip(tail)
                     end
                     if isprompt_paste # remove indentation spaces corresponding to the prompt
-                        tail = replace(tail, r"^ {7}"m, "") # 7: jl_prompt_len
+                        tail = replace(tail, r"^ {7}"m => "") # 7: jl_prompt_len
                     end
                     LineEdit.replace_line(s, tail, true)
                     LineEdit.refresh_line(s)
@@ -956,7 +956,7 @@ function setup_interface(
                 line = strip(input[oldpos:prevind(input, pos)])
                 if !isempty(line)
                     if isprompt_paste # remove indentation spaces corresponding to the prompt
-                        line = replace(line, r"^ {7}"m, "") # 7: jl_prompt_len
+                        line = replace(line, r"^ {7}"m => "") # 7: jl_prompt_len
                     end
                     # put the line on the screen and history
                     LineEdit.replace_line(s, line)
diff --git a/base/repl/REPLCompletions.jl b/base/repl/REPLCompletions.jl
index 345c5a9a8c582..542b66804dd27 100644
--- a/base/repl/REPLCompletions.jl
+++ b/base/repl/REPLCompletions.jl
@@ -192,7 +192,7 @@ function complete_path(path::AbstractString, pos; use_envpath=false)
         end
     end
 
-    matchList = String[replace(s, r"\s", "\\ ") for s in matches]
+    matchList = String[replace(s, r"\s" => "\\ ") for s in matches]
     startpos = pos - endof(prefix) + 1 - length(matchall(r" ", prefix))
     # The pos - endof(prefix) + 1 is correct due to `endof(prefix)-endof(prefix)==0`,
     # hence we need to add one to get the first index. This is also correct when considering
@@ -503,15 +503,15 @@ function completions(string, pos)
         startpos = nextind(partial, reverseind(partial, m.offset))
         r = startpos:pos
 
-        expanded = complete_expanduser(replace(string[r], r"\\ ", " "), r)
+        expanded = complete_expanduser(replace(string[r], r"\\ " => " "), r)
         expanded[3] && return expanded  # If user expansion available, return it
 
-        paths, r, success = complete_path(replace(string[r], r"\\ ", " "), pos)
+        paths, r, success = complete_path(replace(string[r], r"\\ " => " "), pos)
 
         if inc_tag == :string &&
            length(paths) == 1 &&  # Only close if there's a single choice,
            !isdir(expanduser(replace(string[startpos:prevind(string, start(r))] * paths[1],
-                                     r"\\ ", " "))) &&  # except if it's a directory
+                                     r"\\ " => " "))) &&  # except if it's a directory
            (length(string) <= pos ||
             string[nextind(string,pos)] != '"')  # or there's already a " at the cursor.
             paths[1] *= "\""
diff --git a/base/repl/latex_symbols.jl b/base/repl/latex_symbols.jl
index e268b389a644b..a4792522a8e7a 100644
--- a/base/repl/latex_symbols.jl
+++ b/base/repl/latex_symbols.jl
@@ -53,7 +53,7 @@ const latex_strings = Set(values(Base.REPLCompletions.latex_symbols))
 open(fname) do f
     for L in eachline(f)
         x = map(s -> rstrip(s, [' ','\t','\n']),
-                split(replace(L, r"[{}\"]+", "\t"), "\t"))
+                split(replace(L, r"[{}\"]+" => "\t"), "\t"))
         c = Char(parse(Int, x[2], 16))
         if (Base.is_id_char(c) || Base.isoperator(Symbol(c))) &&
            string(c) ∉ latex_strings && !isascii(c)
diff --git a/base/shell.jl b/base/shell.jl
index 0ab8a09f80083..bd362bcb40a93 100644
--- a/base/shell.jl
+++ b/base/shell.jl
@@ -222,11 +222,11 @@ function print_shell_escaped_posixly(io::IO, args::AbstractString...)
             return true
         end
         if all(isword, arg)
-            have_single && (arg = replace(arg, '\'', "\\'"))
-            have_double && (arg = replace(arg, '"', "\\\""))
+            have_single && (arg = replace(arg, '\'' => "\\'"))
+            have_double && (arg = replace(arg, '"' => "\\\""))
             print(io, arg)
         else
-            print(io, '\'', replace(arg, '\'', "'\\''"), '\'')
+            print(io, '\'', replace(arg, '\'' => "'\\''"), '\'')
         end
         first = false
     end
diff --git a/base/strings/util.jl b/base/strings/util.jl
index c709f94ff46b3..9cb8898d465df 100644
--- a/base/strings/util.jl
+++ b/base/strings/util.jl
@@ -373,8 +373,8 @@ _replace(io, repl, str, r, pattern) = print(io, repl)
 _replace(io, repl::Function, str, r, pattern) =
     print(io, repl(SubString(str, first(r), last(r))))
 
-# TODO: rename to `replace` when `replace` is removed from deprecated.jl
-function replace_new(str::String, pattern, repl, count::Integer)
+function replace(str::String, pat_repl::Pair; count::Integer=typemax(Int))
+    pattern, repl = pat_repl
     count == 0 && return str
     count < 0 && throw(DomainError(count, "`count` must be non-negative."))
     n = 1
@@ -407,11 +407,11 @@ function replace_new(str::String, pattern, repl, count::Integer)
 end
 
 """
-    replace(s::AbstractString, pat, r, [count::Integer])
+    replace(s::AbstractString, pat=>r; [count::Integer])
 
 Search for the given pattern `pat` in `s`, and replace each occurrence with `r`.
 If `count` is provided, replace at most `count` occurrences.
-As with [`search`](@ref), the second argument may be a
+As with [`search`](@ref), `pat` may be a
 single character, a vector or a set of characters, a string, or a regular expression. If `r`
 is a function, each occurrence is replaced with `r(s)` where `s` is the matched substring.
 If `pat` is a regular expression and `r` is a `SubstitutionString`, then capture group
@@ -420,20 +420,18 @@ To remove instances of `pat` from `string`, set `r` to the empty `String` (`""`)
 
 # Examples
 ```jldoctest
-julia> replace("Python is a programming language.", "Python", "Julia")
+julia> replace("Python is a programming language.", "Python" => "Julia")
 "Julia is a programming language."
 
-julia> replace("The quick foxes run quickly.", "quick", "slow", 1)
+julia> replace("The quick foxes run quickly.", "quick" => "slow", count=1)
 "The slow foxes run quickly."
 
-julia> replace("The quick foxes run quickly.", "quick", "", 1)
+julia> replace("The quick foxes run quickly.", "quick" => "", count=1)
 "The  foxes run quickly."
 ```
 """
-replace(s::AbstractString, pat, f) = replace_new(String(s), pat, f, typemax(Int))
-# TODO: change this to the following when `replace` is removed from deprecated.jl:
-# replace(s::AbstractString, pat, f, count::Integer=typemax(Int)) =
-#     replace(String(s), pat, f, count)
+replace(s::AbstractString, pat_f::Pair; count=typemax(Int)) =
+    replace(String(s), pat_f, count=count)
 
 # TODO: allow transform as the first argument to replace?
 
diff --git a/doc/src/stdlib/strings.md b/doc/src/stdlib/strings.md
index 04892e3b87e70..74ab2ca518f22 100644
--- a/doc/src/stdlib/strings.md
+++ b/doc/src/stdlib/strings.md
@@ -38,7 +38,7 @@ Base.searchindex
 Base.rsearchindex
 Base.contains(::AbstractString, ::AbstractString)
 Base.reverse(::Union{String,SubString{String}})
-Base.replace(s::AbstractString, pat, f)
+Base.replace(s::AbstractString, ::Pair)
 Base.split
 Base.rsplit
 Base.strip
diff --git a/test/libgit2.jl b/test/libgit2.jl
index 1235cb6d4c88f..83522c4a4cad1 100644
--- a/test/libgit2.jl
+++ b/test/libgit2.jl
@@ -2550,7 +2550,7 @@ mktempdir() do dir
             try
                 # In some environments, namely Macs, the hostname "macbook.local" is bound
                 # to the external address while "macbook" is bound to the loopback address.
-                unshift!(hostnames, replace(gethostname(), r"\..*$", ""))
+                unshift!(hostnames, replace(gethostname(), r"\..*$" => ""))
             end
 
             loopback = ip"127.0.0.1"
diff --git a/test/logging.jl b/test/logging.jl
index fab495d1a86d3..02c10cbfa6f67 100644
--- a/test/logging.jl
+++ b/test/logging.jl
@@ -241,7 +241,7 @@ end
         s = String(take!(io))
         # Remove the small amount of color, as `Base.print_with_color` can't be
         # simply controlled.
-        s = replace(s, r"^\e\[1m\e\[..m(.*)\e\[39m\e\[22m"m, s"\1")
+        s = replace(s, r"^\e\[1m\e\[..m(.*)\e\[39m\e\[22m"m => s"\1")
         # println(s)
         s
     end
diff --git a/test/operators.jl b/test/operators.jl
index 9a883c588d43e..ca020d1910cf4 100644
--- a/test/operators.jl
+++ b/test/operators.jl
@@ -110,8 +110,8 @@ Base.promote_rule(::Type{T19714}, ::Type{Int}) = T19714
 end
 @testset "function negation" begin
     str = randstring(20)
-    @test filter(!Base.Unicode.isupper, str) == replace(str, r"[A-Z]", "")
-    @test filter(!Base.Unicode.islower, str) == replace(str, r"[a-z]", "")
+    @test filter(!Base.Unicode.isupper, str) == replace(str, r"[A-Z]" => "")
+    @test filter(!Base.Unicode.islower, str) == replace(str, r"[a-z]" => "")
 end
 
 # issue #19891
diff --git a/test/perf/shootout/regex_dna.jl b/test/perf/shootout/regex_dna.jl
index 75643153768e9..5a8863040e529 100644
--- a/test/perf/shootout/regex_dna.jl
+++ b/test/perf/shootout/regex_dna.jl
@@ -36,7 +36,7 @@ function regex_dna(infile="regexdna-input.txt")
     seq = read(infile, String)
     l1 = length(seq)
 
-    seq = replace(seq, r">.*\n|\n", "")
+    seq = replace(seq, r">.*\n|\n" => "")
     l2 = length(seq)
 
     for v in variants
@@ -48,7 +48,7 @@ function regex_dna(infile="regexdna-input.txt")
     end
 
     for (u, v) in subs
-        seq = replace(seq, u, v)
+        seq = replace(seq, u => v)
     end
 
 #    println()
@@ -56,4 +56,3 @@ function regex_dna(infile="regexdna-input.txt")
 #    println(l2)
 #    println(length(seq))
 end
-
diff --git a/test/regex.jl b/test/regex.jl
index 3d9837f1c2486..f8e7fd37d6827 100644
--- a/test/regex.jl
+++ b/test/regex.jl
@@ -45,7 +45,7 @@ let m = match(r"(?<a>.)(.)(?<b>.)", "xyz")
 end
 
 # Backcapture reference in substitution string
-@test replace("abcde", r"(..)(?P<byname>d)", s"\g<byname>xy\\\1") == "adxy\\bce"
+@test replace("abcde", r"(..)(?P<byname>d)" => s"\g<byname>xy\\\1") == "adxy\\bce"
 @test_throws ErrorException replace("a", r"(?P<x>)", s"\g<y>")
 
 # Proper unicode handling
diff --git a/test/replcompletions.jl b/test/replcompletions.jl
index a941a417aeff2..497baa63a096d 100644
--- a/test/replcompletions.jl
+++ b/test/replcompletions.jl
@@ -704,7 +704,7 @@ end
 let path = tempdir(),
     space_folder = randstring() * " α",
     dir = joinpath(path, space_folder),
-    dir_space = replace(space_folder, " ", "\\ ")
+    dir_space = replace(space_folder, " " => "\\ ")
 
     mkdir(dir)
     cd(path) do
diff --git a/test/show.jl b/test/show.jl
index b98d113fd96ce..3838f33e02621 100644
--- a/test/show.jl
+++ b/test/show.jl
@@ -302,7 +302,7 @@ end
 
 # issue #7921
 @test replace(sprint(show, Expr(:function, :(==(a, b)), Expr(:block,:(return a == b)))),
-              r"\s+", " ") == ":(function ==(a, b) return a == b end)"
+              r"\s+" => " ") == ":(function ==(a, b) return a == b end)"
 
 # unicode operator printing
 @test sprint(show, :(1 ⊕ (2 ⊗ 3))) == ":(1 ⊕ 2 ⊗ 3)"
@@ -581,7 +581,7 @@ let ex,
     @test string(l2)  == "#= myfile:42 =#"
     @test string(l1)  == string(l2n)
     ex = Expr(:block, l1, :x, l2, :y, l2n, :z)
-    @test replace(string(ex)," ","") == replace("""
+    @test replace(string(ex)," " => "") == replace("""
     begin
         #= line 42 =#
         x
@@ -589,7 +589,7 @@ let ex,
         y
         #= line 42 =#
         z
-    end""", " ", "")
+    end""", " " => "")
 end
 # Test the printing of whatever form of line number representation
 # that is used in the arguments to a macro looks the same as for
diff --git a/test/strings/util.jl b/test/strings/util.jl
index f2d829357a637..97a417fe86e8c 100644
--- a/test/strings/util.jl
+++ b/test/strings/util.jl
@@ -153,110 +153,110 @@ end
 end
 
 @testset "replace" begin
-    @test replace("\u2202", '*', '\0') == "\u2202"
-
-    @test replace("foobar", 'o', '0') == "f00bar"
-    @test replace("foobar", 'o', '0', 1) == "f0obar"
-    @test replace("foobar", 'o', "") == "fbar"
-    @test replace("foobar", 'o', "", 1) == "fobar"
-    @test replace("foobar", 'f', 'F') == "Foobar"
-    @test replace("foobar", 'r', 'R') == "foobaR"
-
-    @test replace("foofoofoo", "foo", "bar") == "barbarbar"
-    @test replace("foobarfoo", "foo", "baz") == "bazbarbaz"
-    @test replace("barfoofoo", "foo", "baz") == "barbazbaz"
-
-    @test replace("", "", "") == ""
-    @test replace("", "", "x") == "x"
-    @test replace("", "x", "y") == ""
-
-    @test replace("abcd", "", "^") == "^a^b^c^d^"
-    @test replace("abcd", "b", "^") == "a^cd"
-    @test replace("abcd", r"b?", "^") == "^a^c^d^"
-    @test replace("abcd", r"b+", "^") == "a^cd"
-    @test replace("abcd", r"b?c?", "^") == "^a^d^"
-    @test replace("abcd", r"[bc]?", "^") == "^a^^d^"
-
-    @test replace("foobarfoo", r"(fo|ba)", "xx") == "xxoxxrxxo"
-    @test replace("foobarfoo", r"(foo|ba)", "bar") == "barbarrbar"
-
-    @test replace("foobar", 'o', 'ø') == "føøbar"
-    @test replace("foobar", 'o', 'ø', 1) == "føobar"
-    @test replace("føøbar", 'ø', 'o') == "foobar"
-    @test replace("føøbar", 'ø', 'o', 1) == "foøbar"
-    @test replace("føøbar", 'ø', 'ö') == "fööbar"
-    @test replace("føøbar", 'ø', 'ö', 1) == "föøbar"
-    @test replace("føøbar", 'ø', "") == "fbar"
-    @test replace("føøbar", 'ø', "", 1) == "føbar"
-    @test replace("føøbar", 'f', 'F') == "Føøbar"
-    @test replace("ḟøøbar", 'ḟ', 'F') == "Føøbar"
-    @test replace("føøbar", 'f', 'Ḟ') == "Ḟøøbar"
-    @test replace("ḟøøbar", 'ḟ', 'Ḟ') == "Ḟøøbar"
-    @test replace("føøbar", 'r', 'R') == "føøbaR"
-    @test replace("føøbaṙ", 'ṙ', 'R') == "føøbaR"
-    @test replace("føøbar", 'r', 'Ṙ') == "føøbaṘ"
-    @test replace("føøbaṙ", 'ṙ', 'Ṙ') == "føøbaṘ"
-
-    @test replace("ḟøøḟøøḟøø", "ḟøø", "bar") == "barbarbar"
-    @test replace("ḟøøbarḟøø", "ḟøø", "baz") == "bazbarbaz"
-    @test replace("barḟøøḟøø", "ḟøø", "baz") == "barbazbaz"
-
-    @test replace("foofoofoo", "foo", "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
-    @test replace("fooƀäṙfoo", "foo", "baz") == "bazƀäṙbaz"
-    @test replace("ƀäṙfoofoo", "foo", "baz") == "ƀäṙbazbaz"
-
-    @test replace("foofoofoo", "foo", "bar") == "barbarbar"
-    @test replace("foobarfoo", "foo", "ƀäż") == "ƀäżbarƀäż"
-    @test replace("barfoofoo", "foo", "ƀäż") == "barƀäżƀäż"
-
-    @test replace("ḟøøḟøøḟøø", "ḟøø", "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
-    @test replace("ḟøøƀäṙḟøø", "ḟøø", "baz") == "bazƀäṙbaz"
-    @test replace("ƀäṙḟøøḟøø", "ḟøø", "baz") == "ƀäṙbazbaz"
-
-    @test replace("ḟøøḟøøḟøø", "ḟøø", "bar") == "barbarbar"
-    @test replace("ḟøøbarḟøø", "ḟøø", "ƀäż") == "ƀäżbarƀäż"
-    @test replace("barḟøøḟøø", "ḟøø", "ƀäż") == "barƀäżƀäż"
-
-    @test replace("ḟøøḟøøḟøø", "ḟøø", "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
-    @test replace("ḟøøƀäṙḟøø", "ḟøø", "ƀäż") == "ƀäżƀäṙƀäż"
-    @test replace("ƀäṙḟøøḟøø", "ḟøø", "ƀäż") == "ƀäṙƀäżƀäż"
-
-    @test replace("", "", "ẍ") == "ẍ"
-    @test replace("", "ẍ", "ÿ") == ""
-
-    @test replace("äƀçđ", "", "π") == "πäπƀπçπđπ"
-    @test replace("äƀçđ", "ƀ", "π") == "äπçđ"
-    @test replace("äƀçđ", r"ƀ?", "π") == "πäπçπđπ"
-    @test replace("äƀçđ", r"ƀ+", "π") == "äπçđ"
-    @test replace("äƀçđ", r"ƀ?ç?", "π") == "πäπđπ"
-    @test replace("äƀçđ", r"[ƀç]?", "π") == "πäππđπ"
-
-    @test replace("foobarfoo", r"(fo|ba)", "ẍẍ") == "ẍẍoẍẍrẍẍo"
-
-    @test replace("ḟøøbarḟøø", r"(ḟø|ba)", "xx") == "xxøxxrxxø"
-    @test replace("ḟøøbarḟøø", r"(ḟøø|ba)", "bar") == "barbarrbar"
-
-    @test replace("fooƀäṙfoo", r"(fo|ƀä)", "xx") == "xxoxxṙxxo"
-    @test replace("fooƀäṙfoo", r"(foo|ƀä)", "ƀäṙ") == "ƀäṙƀäṙṙƀäṙ"
-
-    @test replace("ḟøøƀäṙḟøø", r"(ḟø|ƀä)", "xx") == "xxøxxṙxxø"
-    @test replace("ḟøøƀäṙḟøø", r"(ḟøø|ƀä)", "ƀäṙ") == "ƀäṙƀäṙṙƀäṙ"
-
-    @test replace("foo", "oo", Base.Unicode.uppercase) == "fOO"
+    @test replace("\u2202", '*' => '\0') == "\u2202"
+
+    @test replace("foobar", 'o' => '0') == "f00bar"
+    @test replace("foobar", 'o' => '0', count=1) == "f0obar"
+    @test replace("foobar", 'o' => "") == "fbar"
+    @test replace("foobar", 'o' => "", count=1) == "fobar"
+    @test replace("foobar", 'f' => 'F') == "Foobar"
+    @test replace("foobar", 'r' => 'R') == "foobaR"
+
+    @test replace("foofoofoo", "foo" => "bar") == "barbarbar"
+    @test replace("foobarfoo", "foo" => "baz") == "bazbarbaz"
+    @test replace("barfoofoo", "foo" => "baz") == "barbazbaz"
+
+    @test replace("", "" => "") == ""
+    @test replace("", "" => "x") == "x"
+    @test replace("", "x" => "y") == ""
+
+    @test replace("abcd", "" => "^") == "^a^b^c^d^"
+    @test replace("abcd", "b" => "^") == "a^cd"
+    @test replace("abcd", r"b?" => "^") == "^a^c^d^"
+    @test replace("abcd", r"b+" => "^") == "a^cd"
+    @test replace("abcd", r"b?c?" => "^") == "^a^d^"
+    @test replace("abcd", r"[bc]?" => "^") == "^a^^d^"
+
+    @test replace("foobarfoo", r"(fo|ba)" => "xx") == "xxoxxrxxo"
+    @test replace("foobarfoo", r"(foo|ba)" => "bar") == "barbarrbar"
+
+    @test replace("foobar", 'o' => 'ø') == "føøbar"
+    @test replace("foobar", 'o' => 'ø', count=1) == "føobar"
+    @test replace("føøbar", 'ø' => 'o') == "foobar"
+    @test replace("føøbar", 'ø' => 'o', count=1) == "foøbar"
+    @test replace("føøbar", 'ø' => 'ö') == "fööbar"
+    @test replace("føøbar", 'ø' => 'ö', count=1) == "föøbar"
+    @test replace("føøbar", 'ø' => "") == "fbar"
+    @test replace("føøbar", 'ø' => "", count=1) == "føbar"
+    @test replace("føøbar", 'f' => 'F') == "Føøbar"
+    @test replace("ḟøøbar", 'ḟ' => 'F') == "Føøbar"
+    @test replace("føøbar", 'f' => 'Ḟ') == "Ḟøøbar"
+    @test replace("ḟøøbar", 'ḟ' => 'Ḟ') == "Ḟøøbar"
+    @test replace("føøbar", 'r' => 'R') == "føøbaR"
+    @test replace("føøbaṙ", 'ṙ' => 'R') == "føøbaR"
+    @test replace("føøbar", 'r' => 'Ṙ') == "føøbaṘ"
+    @test replace("føøbaṙ", 'ṙ' => 'Ṙ') == "føøbaṘ"
+
+    @test replace("ḟøøḟøøḟøø", "ḟøø" => "bar") == "barbarbar"
+    @test replace("ḟøøbarḟøø", "ḟøø" => "baz") == "bazbarbaz"
+    @test replace("barḟøøḟøø", "ḟøø" => "baz") == "barbazbaz"
+
+    @test replace("foofoofoo", "foo" => "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
+    @test replace("fooƀäṙfoo", "foo" => "baz") == "bazƀäṙbaz"
+    @test replace("ƀäṙfoofoo", "foo" => "baz") == "ƀäṙbazbaz"
+
+    @test replace("foofoofoo", "foo" => "bar") == "barbarbar"
+    @test replace("foobarfoo", "foo" => "ƀäż") == "ƀäżbarƀäż"
+    @test replace("barfoofoo", "foo" => "ƀäż") == "barƀäżƀäż"
+
+    @test replace("ḟøøḟøøḟøø", "ḟøø" => "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
+    @test replace("ḟøøƀäṙḟøø", "ḟøø" => "baz") == "bazƀäṙbaz"
+    @test replace("ƀäṙḟøøḟøø", "ḟøø" => "baz") == "ƀäṙbazbaz"
+
+    @test replace("ḟøøḟøøḟøø", "ḟøø" => "bar") == "barbarbar"
+    @test replace("ḟøøbarḟøø", "ḟøø" => "ƀäż") == "ƀäżbarƀäż"
+    @test replace("barḟøøḟøø", "ḟøø" => "ƀäż") == "barƀäżƀäż"
+
+    @test replace("ḟøøḟøøḟøø", "ḟøø" => "ƀäṙ") == "ƀäṙƀäṙƀäṙ"
+    @test replace("ḟøøƀäṙḟøø", "ḟøø" => "ƀäż") == "ƀäżƀäṙƀäż"
+    @test replace("ƀäṙḟøøḟøø", "ḟøø" => "ƀäż") == "ƀäṙƀäżƀäż"
+
+    @test replace("", "" => "ẍ") == "ẍ"
+    @test replace("", "ẍ" => "ÿ") == ""
+
+    @test replace("äƀçđ", "" => "π") == "πäπƀπçπđπ"
+    @test replace("äƀçđ", "ƀ" => "π") == "äπçđ"
+    @test replace("äƀçđ", r"ƀ?" => "π") == "πäπçπđπ"
+    @test replace("äƀçđ", r"ƀ+" => "π") == "äπçđ"
+    @test replace("äƀçđ", r"ƀ?ç?" => "π") == "πäπđπ"
+    @test replace("äƀçđ", r"[ƀç]?" => "π") == "πäππđπ"
+
+    @test replace("foobarfoo", r"(fo|ba)" => "ẍẍ") == "ẍẍoẍẍrẍẍo"
+
+    @test replace("ḟøøbarḟøø", r"(ḟø|ba)" => "xx") == "xxøxxrxxø"
+    @test replace("ḟøøbarḟøø", r"(ḟøø|ba)" => "bar") == "barbarrbar"
+
+    @test replace("fooƀäṙfoo", r"(fo|ƀä)" => "xx") == "xxoxxṙxxo"
+    @test replace("fooƀäṙfoo", r"(foo|ƀä)" => "ƀäṙ") == "ƀäṙƀäṙṙƀäṙ"
+
+    @test replace("ḟøøƀäṙḟøø", r"(ḟø|ƀä)" => "xx") == "xxøxxṙxxø"
+    @test replace("ḟøøƀäṙḟøø", r"(ḟøø|ƀä)" => "ƀäṙ") == "ƀäṙƀäṙṙƀäṙ"
+
+    @test replace("foo", "oo" => Base.Unicode.uppercase) == "fOO"
 
     # Issue 13332
-    @test replace("abc", 'b', 2.1) == "a2.1c"
+    @test replace("abc", 'b' => 2.1) == "a2.1c"
 
     # test replace with a count for String and GenericString
     # check that replace is a no-op if count==0
     for s in ["aaa", Test.GenericString("aaa")]
-        # @test replace("aaa", 'a', 'z', 0) == "aaa" # enable when undeprecated
-        @test replace(s, 'a', 'z', 1) == "zaa"
-        @test replace(s, 'a', 'z', 2) == "zza"
-        @test replace(s, 'a', 'z', 3) == "zzz"
-        @test replace(s, 'a', 'z', 4) == "zzz"
-        @test replace(s, 'a', 'z', typemax(Int)) == "zzz"
-        @test replace(s, 'a', 'z')    == "zzz"
+        # @test replace("aaa", 'a' => 'z', count=0) == "aaa" # enable when undeprecated
+        @test replace(s, 'a' => 'z', count=1) == "zaa"
+        @test replace(s, 'a' => 'z', count=2) == "zza"
+        @test replace(s, 'a' => 'z', count=3) == "zzz"
+        @test replace(s, 'a' => 'z', count=4) == "zzz"
+        @test replace(s, 'a' => 'z', count=typemax(Int)) == "zzz"
+        @test replace(s, 'a' => 'z')    == "zzz"
     end
 end
 
diff --git a/test/testdefs.jl b/test/testdefs.jl
index 3191d553cb193..c6af76df2b8c8 100644
--- a/test/testdefs.jl
+++ b/test/testdefs.jl
@@ -9,7 +9,7 @@ function runtests(name, path, isolate=true; seed=nothing)
         if isolate
             # Simple enough to type and random enough so that no one will hard
             # code it in the test
-            mod_name = Symbol("Test", rand(1:100), "Main_", replace(name, '/', '_'))
+            mod_name = Symbol("Test", rand(1:100), "Main_", replace(name, '/' => '_'))
             m = @eval(Main, module $mod_name end)
         else
             m = Main