repeat with repeat will loop endlessly

[muja]

line = (match('$').absent? >> any).repeat >> match('$')
line.parse("Hello world!") # => "Hello world!"@0
line.parse("Hello world!\n") # => "Hello world!\n"@0
line.repeat.parse("Hello\nThis\nis\na\nmultiline\nstring.") # never returns

[kschiess]

Yes. Both repeats will accept a zero width match. The first one doesn't consume anything, the second one repeats that success.