#!/usr/bin/perl --

use strict;
use warnings;

Main();
exit(0);

sub Main {
    my @a;
    for ( 0 .. 10 ) {
        print Dumpyh( @a = yh(@a) );
    }
} ## end sub Main

sub yh {
    my (@a) = @_;
    my @b = (1);

#~     for ( my $i = 1 ; $i < @a ; $i++ ) {
    for my $i ( 1 .. $#a ) {
        $b[$i] = $a[$i] + $a[ $i - 1 ];
    }
    $b[@a] = 1;
    return @b;
} ## end sub yh

sub Dumpyh {

#~     return @_, "\n";
#~     return "@_\n";
    my $s = "@_";
    join '', ' ' x ( abs( 40 - length $s ) / 2 ), "$s\n";
} ## end sub Dumpyh

__END__

                   1
                  1 1
                 1 2 1
                1 3 3 1
               1 4 6 4 1
             1 5 10 10 5 1
            1 6 15 20 15 6 1
          1 7 21 35 35 21 7 1
         1 8 28 56 70 56 28 8 1
      1 9 36 84 126 126 84 36 9 1
  1 10 45 120 210 252 210 120 45 10 1