Here are a few examples on how to use regular expressions in Elixir.

# A regex sigil to match 'foo'
~r/foo/

# Interpolation can be used
~r/foo/ = ~r/#{"foo"}/

# Test if a string matches
true = Regex.match?( ~r/foo/ , "Hello foo")

# Run returns first match
["foo1", "1"] = Regex.run(~r/foo([0-9])/, "foo1 foo2")

# Scan returns all matches
[["foo1", "1"], ["foo2", "2"]] = Regex.scan(~r/foo([0-9])/, "foo1 foo2")

# Replace matches in a string
"one_two_three" = Regex.replace(~r/-/, "one-two-three", "_")

Documentation: Regex