First stab at supporting :16<DEADBEEF> style numbers.

src/Perl6/Actions.pm

@@ -2086,6 +2086,7 @@ method number:sym<numish>($/) {
 method numish($/) {
     if $<integer> { make PAST::Val.new( :value($<integer>.ast) ); }
     elsif $<dec_number> { make $<dec_number>.ast; }
+    elsif $<rad_number> { make $<rad_number>.ast; }
     else {
         make PAST::Var.new( :name(~$/), :namespace(''), :scope('package') );
     }
@@ -2127,6 +2128,18 @@ method dec_number($/) {
     }
 }
 
+method rad_number($/) {
+    my $radix    := +($<radix>.Str);
+    my $intpart  := $<intpart>.Str;
+    my $fracpart := $<fracpart> ?? $<fracpart>.Str !! "0";
+    my $base     := $<base> ?? $<base>.ast !! 0;
+    my $exp      := $<exp> ?? $<exp>.ast !! 0;
+
+    make PAST::Op.new( :name('&radcalc'), :pasttype('call'),
+        $radix, $intpart, $fracpart, $base, $exp
+    );
+}
+
 method typename($/) {
     my $past;
 

src/Perl6/Grammar.pm

@@ -938,7 +938,7 @@ token numish {
     [
     | <dec_number>
     | <integer>
-#    | <rad_number>
+    | <rad_number>
     | 'NaN' >>
     | 'Inf' >>
     | '+Inf' >>
@@ -952,6 +952,33 @@ token dec_number {
     | $<coeff> = [ <int=.decint>                    ] <escale>
 }
 
+token rad_number {
+     <!before '::'> ':' $<radix> = [\d+] <.unsp>?
+    # {}           # don't recurse in lexer
+    # :dba('number in radix notation')
+    [
+    || '<'
+            $<intpart> = [ <[ 0..9 a..z A..Z ]>+ [ _ <[ 0..9 a..z A..Z ]>+ ]* ]
+            $<fracpart> = [ '.' <[ 0..9 a..z A..Z ]>+ [ _ <[ 0..9 a..z A..Z ]>+ ]* ]?
+            [ '*' <base=.radint> '**' <exp=.radint> ]?
+       '>'
+    # || <?before '['> <circumfix>
+    # || <?before '('> <circumfix>
+    || <.panic: "Malformed radix number">
+    ]
+}
+
+token radint {
+    [
+    | <integer>
+    # | <?before ':'\d> <rad_number> <?{
+    #                         defined $<rad_number><intpart>
+    #                         and
+    #                         not defined $<rad_number><fracpart>
+    #                     }>
+    ]
+}
+
 token escale { <[Ee]> $<sign>=[<[+\-]>?] <decint> }
 
 token typename {

src/builtins/Num.pir

@@ -117,6 +117,84 @@ Value type, so return self.
 
 =cut
 
+=item radcalc
+
+=cut
+
+.namespace []
+
+.sub '&radcalc'
+    .param int radix
+    .param string intpart
+    .param string fracpart     :optional
+    .param int    has_fracpart :opt_flag
+    .param num    base         :optional
+    .param int    has_base     :opt_flag
+    .param num    exp          :optional
+    .param int    has_exp      :opt_flag
+    .local num    result, fracdivisor, magnitude
+    .local pmc    it
+
+    if radix <= 1 goto err_range
+    if radix > 36 goto err_range
+
+    result       = 0.0
+    fracdivisor = 1.0
+
+    $P0 = split '', intpart
+    it = iter $P0
+
+  lp1: # Accumulate over decimal part
+    unless it goto ex1
+    $S0 = shift it
+    $S0 = downcase $S0
+    if $S0 == "_" goto lp1
+    $I0 = index "0123456789abcdefghijklmnopqrstuvwxyz", $S0
+    if $I0 == -1 goto err_char
+    $N0 = $I0
+    result *= radix
+    result += $N0
+    goto lp1
+
+  ex1:
+    unless has_fracpart goto nofracpart
+    $I0 = length fracpart
+    unless $I0 goto nofracpart
+    $P0 = split '', fracpart
+    $P99 = shift $P0                             # remove the radix point
+
+  lp2: # Accumulate over fractional part, keep length
+    unless it goto ex2
+    $S0 = shift it
+    $S0 = downcase $S0
+    if $S0 == "_" goto lp2
+    $I0 = index "0123456789abcdefghijklmnopqrstuvwxyz", $S0
+    if $I0 == -1 goto err_char
+    $N0 = $I0
+
+    result *= radix
+    result += $N0
+    fracdivisor *= radix
+    goto lp2
+
+  ex2:
+    result /= fracdivisor
+
+  nofracpart:
+    unless has_base goto ret
+    magnitude = base ** exp
+    result *= magnitude
+  ret:
+    .return (result)
+
+  err_range:
+    die "radix out of range (2-36)"
+  err_char:
+    $S0 = concat "unrecognized character: ", $S0
+    die $S0
+.end
+
+
 # Local Variables:
 #   mode: pir
 #   fill-column: 100