How do you calculate div and mod of floating point numbers

sub foo {
    my $n1 = shift;
    my $n2 = shift;
    print "perl's mod=" . $n1 % $n2, "n";
    my $res = $n1 / $n2;
    my $t = int($res);
    print "my div=$t", "n";
    $res = $res - $t;
    $res = $res * $n2;
    print "my mod=" . $res . "nn";
}

foo( 3044.952963, 7.1 );
foo( 3044.952963, -7.1 );
foo( -3044.952963, 7.1 );
foo( -3044.952963, -7.1 );

perl's mod=6
my div=428
my mod=6.15296300000033

perl's mod=-1
my div=-428
my mod=6.15296300000033

perl's mod=1
my div=-428
my mod=-6.15296300000033

perl's mod=-6
my div=428
my mod=-6.15296300000033

use POSIX "fmod";

sub foo {
    my $n1 = shift;
    my $n2 = shift;
    print "perl's fmod=" . fmod($n1,$n2), "n";
    my $res = $n1 / $n2;
    my $t = int($res);
    print "my div=$t", "n";
    $res = $res - $t;
    $res = $res * $n2;
    print "my mod=" . $res . "nn";
}

foo( 3044.952963, 7.1 );
foo( 3044.952963, -7.1 );
foo( -3044.952963, 7.1 );
foo( -3044.952963, -7.1 );

perl's fmod=6.15296300000033
my div=428
my mod=6.15296300000033

perl's fmod=6.15296300000033
my div=-428
my mod=6.15296300000033

perl's fmod=-6.15296300000033
my div=-428
my mod=-6.15296300000033

perl's fmod=-6.15296300000033
my div=428
my mod=-6.15296300000033