use PDL::Apply 'apply_rolling';

sub sms_WxH_PDL_ar ( $m, $w, $h ) {
    $m-> apply_rolling( $w, 'sum' )
      -> slice( [ $w - 1, -1 ], [] )
      -> xchg( 0, 1 )
      -> apply_rolling( $h, 'sum' )
      -> slice( [ $h - 1, -1 ], [] )
      -> xchg( 0, 1 )
}

my $m = random 150, 150;
$t = time;
sms_WxH_PDL_ar( $m, 2, 2 );
say time - $t;
$t = time;
sms_WxH_PDL_ar( $m, 10, 10 );
say time - $t;
$t = time;
sms_WxH_PDL_ar( $m, 75, 75 );
say time - $t;

__END__

3.36784410476685
3.20836806297302
1.28170394897461