`Longest[p]` tries the longest split of a sequence pattern first; the default
與 .wl 參考的差異： `Longest`/`Shortest` in a definition
Longest[p]
{1, 2, 3} /. {Longest[x__], y__} :> {{x}, {y}}
→ {{1, 2}, {3}}{1, 2, 3} /. {Shortest[x__], y__} :> {{x}, {y}}
→ {{1}, {2, 3}}{{1, 2, 3} /. {Longest[x_], ___} :> x, MatchQ[{1, 2}, {Longest[__], _}]}
→ {1, True}