Customary  Generic        Meaning        Interpolates
    ''       q{}          Literal             no
    ""      qq{}          Literal             yes
    ``      qx{}          Command             yes*
            qw{}         Word list            no
    //       m{}       Pattern match          yes*
            qr{}          Pattern             yes*
             s{}{}      Substitution          yes*
            tr{}{}    Transliteration         no (but see below)
             y{}{}    Transliteration         no (but see below)
    <<EOF                 here-doc            yes*

    * unless the delimiter is ''.