A work in progress PCRE for matching [AWS EventBridge scheduling expressions](https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-cron-expressions.html). See it in action [on RegExr](https://regexr.com/7t6id).

aws-schedule-expressions.pl

# the whole enchilada...
/
^
(
    rate\(
        (
            (
                1[ ]+(hour|minute|day))
                |
                ([0-9]+[ ]+(hours|minutes|days)
            )
        )
    \)
)
|
(
    cron\(

        # minutes field
        (?:
            (?:
                (?:
                    [0-5]?
                    [0-9]
                )
                |
                [*]
            )
            [,/-]?
        ){1,}

        [ ]+

        # hours field
        (?:
            (?:
                (?:
                    [0-2]?
                    [0-9]
                )
                |
                [*]
            )
            [,/-]?
        ){1,}

        [ ]+

        # day of month field
        (?:
            (?:
                (?:
                    [1-3]?
                    [0-9]
                )
                |
                [LW*?]
            )
            [,/-]?
        ){1,}

        [ ]+

        # month field
        (?:
            (?:
                (?:
                    [1]?
                    [0-9]
                )
                |
                (?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)
                |
                [*]
            )
            [,/-]?
        ){1,}

        [ ]+

        # day of week field
        (?:
            (?:
                [1-7]
                |
                (?:SUN|MON|TUE|WED|THU|FRI|SAT)
                |
                [L*?]
            )
            [#,/-]?
        ){1,}

        [ ]+

        # year field
        (?:
            (?:
                (?:
                    [12]
                    [0-9]{3}
                )
                |
                [*]
            )
            [,/-]?
        ){1,}

    \)
)
$
/x;


# each cron field broken out for clarity and debugging purposes...
/
    # minutes field
    (?:
        (?:
            (?:
                [0-5]?
                [0-9]
            )
            |
            [*]
        )
        [,/-]?
    ){1,}
/x;

/
    # hours field
    (?:
        (?:
            (?:
                [0-2]?
                [0-9]
            )
            |
            [*]
        )
        [,/-]?
    ){1,}
/x;

/
    # day of month field
    (?:
        (?:
            (?:
                [1-3]?
                [0-9]
            )
            |
            [LW*?]
        )
        [,/-]?
    ){1,}
/x;

/
    # month field
    (?:
        (?:
            (?:
                [1]?
                [0-9]
            )
            |
            (?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)
            |
            [*]
        )
        [,/-]?
    ){1,}
/x;

/
    # day of week field
    (?:
        (?:
            [1-7]
            |
            (?:SUN|MON|TUE|WED|THU|FRI|SAT)
            |
            [L*?]
        )
        [#,/-]?
    ){1,}
/x;

/
    # year field
    (?:
        (?:
            (?:
                [12]
                [0-9]{3}
            )
            |
            [*]
        )
        [,/-]?
    ){1,}
/x;


# Field			Values				Wildcards
# Minutes		0-59				, - * /
# Hours			0-23				, - * /
# Day-of-month	1-31				, - * ? / L W
# Month			1-12 or JAN-DEC		, - * /
# Day-of-week	1-7 or SUN-SAT		, - * ? L #
# Year			1970-2199			, - * /

# Additional restrictions (not yet implemented)
# 1. Day-of-week, if you use a '#' character, you can define only one expression in the day-of-week field. For example, "3#1,6#3" is not valid because it is interpreted as two expressions.
# 2. You can't specify the Day-of-month and Day-of-week fields in the same cron expression. If you specify a value or a * (asterisk) in one of the fields, you must use a ? (question mark) in the other.
# ^^ May be able to implement these with look-(behind|ahead)? ...this one's gonna be complex