x.pl

    proto token constant { * }

    # int
    token constant:sym<int>  { <int-lit> }
    proto token int-lit { * }
    token int-lit:sym<dec>   { '-'? <[1..9]>\d* }
    token int-lit:sym<hex>   { '-'? '0' <[xX]> <.xdigit>+ }
    token int-lit:sym<oct>   { '-'? '0' <[0..7]>* }

    # other numbers
    token constant:sym<float>    { '-'? \d+ '.'? [\d+]? [<[eE]> ['+'|'-']? \d+]? }
    token constant:sym<bool>     { 'true' | 'false' }

    # string
    token constant:sym<str>             { <str-lit> }
    proto token str-lit                 { * }
    token str-lit:sym<single-quoted>    { \' ~ \' ( <-[\\\x00\n']>+ | <str-escape> )* }
    token str-lit:sym<double-quoted>    { \" ~ \" ( <-[\\\x00\n"]>+ | <str-escape> )* }