- Added solutions by Mark Senn.

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diff --git a/challenge-026/mark-senn/perl6/ch-1.p6 b/challenge-026/mark-senn/perl6/ch-1.p6
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+# Perl  Weekly  Challenge  - 026
+# Task #1
+#
+# See
+#      engineering.purdue.edu/~mark/pwc -026 -1. pdf
+# for  more  information.
+#
+# The  command  line  should be, for  example ,
+#      perl6 t.p6  stones  jewels
+# The  values  for "stones" and "jewels"
+# default  to "chancellor" and "chocolate ".
+#
+#
+
+# Run  using  Perl v6.d;
+use v6.d;
+
+sub  MAIN($a = 'chancellor', $b = 'chocolate')
+{
+    # Check  that$a and$b  consist  of only  upper  and  lowerccase  letters.
+    ($a ~~ /^^<[A..Za..z]>+$$/)   or   die qq/"$a" must  consist  of one or more  letters /;
+    ($b ~~ /^^<[A..Za..z]>+$$/)   or   die qq/"$a" must  consist  of one or more  letters /;
+
+    # Convert$a and$b to  arrays.
+    my @a =$a.comb (/./).unique;
+    my @b =$b.comb (/./);
+
+
+    #
+    #    Array -based  solution.
+    #
+
+    # If keys to a hash  can be  expressed  as small
+    # non -negative  integers  you may  want to use an
+    # array  instead  of a hash.
+    my @in -a;
+    @a.map({@in -a[$_.ord] = True });
+    $count = 0;
+    @b.map({@in -a[$_.ord] and $count++});
+    $count.say;
+
+
+    #
+    #   Cross -product  based  solution.
+    #
+
+    $count = 0;
+    (@a X @b).map({$_[0] eq $_[1] and $count++});
+    $count.say;
+
+
+    #
+    #   Hash -based  solution.
+    #
+
+    # Make a %a hash  with  letter  keys  and  True  values.
+    # The  letters  in %a are the  ones we count  in$b.
+    my %a = @a.map({$_ => True });
+
+    # Count  the  characters  in$b that  occur  in$a.
+    my $count = 0;
+    @b.map ({%a{$_} and $count++});
+
+    $count.say;
+
+
+    #
+    #   Set -based  solution.
+    #
+
+    # When I was  looking  up "perl6  degrees  to  radians" to see if there  was
+    # a built -in Perl 6 method  to do it I came  across
+    #      http :// blogs.perl.org/users/laurent_r /2019/09/
+    #      perl -weekly -challenge -26-common -letters -and -mean -angles.html
+    # showing  how to  convert a list/array  to a set.
+    # I like  Laurent  Rosenfeld's solution  better  than  any I did  above.
+    # The  following  is based  on his  work.
+    my $aset = @a.Set;
+    $count = @b.grep({$_ (elem) $aset }).elems;
+    $count.say;
+}
+
diff --git a/challenge-026/mark-senn/perl6/ch-2.p6 b/challenge-026/mark-senn/perl6/ch-2.p6
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+++ b/challenge-026/mark-senn/perl6/ch-2.p6
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+#
+# Perl  Weekly  Challenge  - 026
+# Task #2
+#
+# See
+#      engineering.purdue.edu/~mark/pwc -026 -2. pdf
+# for  more  information.
+#
+# The  command  line  should be, for  example ,
+#      perl6 t.p6 1 2 3
+# to get the  mean  angle  of 1, 2, and 3 degrees.
+#
+
+# Run  using  Perl v6.d;
+use v6.d;
+
+sub  MAIN(*@deg  where  @deg.elems > 0)
+{
+    # Convert  from  degrees  to  radians.
+    my @rad = @deg  <<*>> (pi /180);
+
+    # Transform  from  degrees  to polar  coordinates.
+    my  Complex  @z = @rad.map({e**(i *$_)});
+
+    # Compute$p -bar in  polar  coordinates.
+    my$p -bar = ([+] @z) / @z.elems;
+
+    # Compute  arctangent  and  convert  from  radians  to  degrees.
+    # Sample  inputs  and  outputs:
+    #       INPUT          OUTPUT                           COMMENT
+    #       ----------     -----------------------          -------
+    #          1    1           1
+    #          1    2           1.5
+    #          1    2   3       2
+    #         10  -10           0
+    #         10   20   30      19.999999999999996          wrong
+    #         60                59.99999999999999           wrong
+    #         350   10          -1.614809932057922e-15      wrong
+    my$theta -bar = atan2($p -bar.im ,$p -bar.re) * (180/pi);
+    $theta -bar.say;
+}