my @x = (4, 5, 6, 7, 8, 9, 10);

# Predicate "is even"
sub P {
    return $_ % 2 == 0;
}
# Transformation "square"
sub T{
    return $_*$_;
}
my @y = map { T($_) } grep { P($_) } @x;

print join(',',@y);

16,36,64,100