use Data::Dumper;

print Dumper
    map { my $a=$_;
          map { my $b=$_;
                map { $a**2 == $b **2 + $_ **2
                        ?  [ $_, $b, $a ]
                        :  ()
                } (1..$b)
            } (1..$a)
        } (1..10);


print Dumper
    grep { $_->[0]**2 == $_->[1] **2 + $_->[2] **2 }
        map { my $a=$_;
            map { my $b=$_;
                map {
                    [ $a, $b, $_ ]
                } (1..$b)
            } (1..$a)
        } (1..10);