Text substitution (like sed) with Julia

General Usage
1

If I want to replace all occurrences of “apple” by “orange” in a file, I can use the Unix shell command

sed -i 's/apple/orange/g' filename.txt

What would be an equivalent Julia code?

2

Start with Strings · The Julia Language

3

maybe create a regex literal r"<regex>", like this:

julia> occursin(r"(?i)apple|orange", "Orange or Apple")
true

julia> replace("Orange or Apple", r"(?i)apple" => "Orange")
"Orange or Orange"

Or even fancier:

julia> replace("Orange or Apple", r"(?i)apple" => titlecase("orange"))
"Orange or Orange"