prepend function (See related posts)

    prepend: func [
        {Inserts a value at the head of a series and returns the series head.}
        series [series! port!]
        value
        /only "Prepends a block value as a block"
    ][
        head either only [
            insert/only head series :value
        ] [
            insert head series :value
        ]
    ]