$ perl -E 'my ($s, $e) = qw{" "}; qq{a"b\n"c} =~ /$s([^$e]*)/; say "|$1|"'
|b
|
$ perl -E 'my ($s, $e) = qw{" "}; qq{a"b\n"c} =~ /$s(.*?)$e/; say "|$1|"'
||
$ perl -E 'my ($s, $e) = qw{" "}; qq{a"b\n"c} =~ /$s(.*?)$e/s; say "|$1|"'
|b
|