Bug Report

The expected behaviour when using a MULTILINE regex like #.*$ is that it will match a whole line that begins with #

Because crystal conflates MULTILINE and DOT_ALL, that regex will, when set to MULTILINE, match also any subsequent lines until the end of the file.

Regex.new("#.*$", Regex::Options::MULTILINE).match("# this should be matched\nthis shouldn't")

=> Regex::MatchData("# this should be matched\nthis shouldn't")

To keep backwards compatibility, the behaviour of MULTILINE in crystal should not be changed, but I propose a change that adds a new MULTILINE_ONLY flag that just doesn't set DOT_ALL when creating the underlying PCRE2 object.