My take

#! perl -slw
use strict;
use List::Util qw[ sum ];

sub Cnr{
    my( $n, @r ) = shift;
    return [] unless $n--;
    for my $x ( 0 .. ($#_ - $n) ) {
        push @r, map{ 
            [ $_[$x], @$_ ] 
        } Cnr( $n, @_[ ($x + 1) .. $#_ ] );
    }
    return @r;
}

sub sums{ 
    my( $required, @values ) = @_;
    return grep{
        sum( @$_ ) == $required
        ? $_
        : ()
    } map{ 
        Cnr( $_, @values ) 
    } 1 .. $#values;
}

print "@$_" for sums( 20, 1 .. 9 );
<STDIN>;
__END__
P:\test>355455
3 8 9
4 7 9
5 6 9
5 7 8
1 2 8 9
1 3 7 9
1 4 6 9
1 4 7 8
1 5 6 8
2 3 6 9
2 3 7 8
2 4 5 9
2 4 6 8
2 5 6 7
3 4 5 8
3 4 6 7
1 2 3 5 9
1 2 3 6 8
1 2 4 5 8
1 2 4 6 7
1 3 4 5 7
2 3 4 5 6
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