Hmm.. I could not help it, but this example and the code below might help you a bit more:

#!/usr/bin/perl -w

use strict;
use SDL::App;
use SDL::Rect;
use SDL::Color;
use SDL::Event;

my $app = SDL::App->new(
                -width  => 640,
                -height => 480,
                -depth  => 16,
                -title  => 'My COOL Perl-SDL application.',
        );

my $rect = SDL::Rect->new(
                -height => 100,
                -width  => 100,
                -x      => 0,
                -y      => 0,
        );

my $oldRect = SDL::Rect->new(
                -height => 100,
                -width  => 100,
                -x      => 0,
                -y      => 0,
        );

my @color;
$color[0] = SDL::Color->new( -r => 0x00, -g => 0x00, -b => 0x00, );
$color[1] = SDL::Color->new( -r => 0xff, -g => 0x00, -b => 0x00, );
$color[2] = SDL::Color->new( -r => 0x00, -g => 0xff, -b => 0x00, );
$color[3] = SDL::Color->new( -r => 0x00, -g => 0x00, -b => 0xff, );
$app->fill( $rect, $color[1] );
$app->update( $rect );

my $bgcolor = $color[0];
my $col = 1;
my $fgcolor = $color[$col];

sub draw_frame {
        my (%args) = @_;
        $app->fill( $oldRect, $bgcolor);
        $app->fill( $rect, $fgcolor );
        $app->update( $oldRect, $rect );
}

sub move() {
        my ($x,$y) = @_;
        $rect->x( $x );
        $rect->y( $y );
        draw_frame();
        $oldRect->x( $x );
        $oldRect->y( $y );
}

sub key {
        my $key = shift;
        my $name = $key->key_name;
        print "Key Pressed: $name\n";
        my $x=$rect->x;
        my $y=$rect->y;
        if ($name eq "left") {
                $x -= 10;
                $x = 540 if $x < 0;
                &move($x,$y);
        } elsif ($name eq "right") {
                $x += 10;
                $x = 0 if $x > 540;
                &move($x,$y);
        } elsif ($name eq "up") {
                $y -= 10;
                $y = 380 if $y < 0;
                &move($x,$y);
        } elsif ($name eq "down") {
                $y += 10;
                $y = 0 if $y > 380;
                &move($x,$y);
        } elsif ($name eq "c") {
                $col++;
                $col = 1 if $col > 3;
                $fgcolor = $color[$col];
                draw_frame();
        } elsif ($name eq "q") {
                exit(0);
        }
}

my %actions = (
        SDL_QUIT()      => sub { exit(0); },
        SDL_KEYDOWN()   => \&key,
        );

$app->loop(\%actions);
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