foo /bar/

%r{abc}i

/a\b/

/aaa #$bbb/

/aaa #{bbb} ccc/

[/(?<foo>bar)/ =~ baz, foo]

/abc/i

%r/[a-z$._?][\w$.?#@~]*:/i

%r/([a-z$._?][\w$.?#@~]*)(\s+)(equ)/i

%r/[a-z$._?][\w$.?#@~]*/i

%r(
(?:[#$%_']|\(\)|\(,\)|\[\]|[0-9])*
  (?:[#$%_']+)
)

/(?#\))/ =~ "hi"

%r#pound#

/aaa #{bbb}/o

/(?<a\
b>)/ =~ ""; ab

/(?<abc>)(?<abc>)/ =~ ""; abc

/(?<a b>)/ =~ ""

a = 1
tap { /(?<a>)/ =~ to_s }

/(?<foo>)/ =~ ""
/(?<Foo>)/ =~ ""

/(?<nil>)/ =~ ""
def foo(nil:) = /(?<nil>)/ =~ ""