from typing import Optional


def corner_matcher(entrances_exits: list[bool]) -> Optional[dict]:
    """Check existence and rotation of a corner"""
    if entrances_exits.count(True) != 2:
        return None

    sequence = [True] * 2 + [False] * 2
    for index in range(4):
        if sequence == entrances_exits:
            return {
                "type": "corner",
                "rotation": 90 * index
            }
        sequence = sequence[-1:] + sequence[:-1]

    return None