$winMain->Hook(
    WM_MEASUREITEM,
    sub {
        my($self, $wParam, $lParam, $type, $msgcode) = @_;
        return 1 unless $type == 0;
        return 1 unless $msgcode == WM_MEASUREITEM;
        my %measureitem;
        # Unpack data from structure
        @measureitem{qw(CtrlType CtrlID itemID itemWidth itemHeight itemData)} = 
            unpack 'IIIIIL', unpack 'P24', pack 'L', $lParam;
        # Set the height of the items
        $measureitem{'itemHeight'} = 30;
        # Pack data back into structure
        my $struct = pack 'IIIIIL',
            @measureitem{qw(CtrlType CtrlID itemID itemWidth itemHeight itemData)};
        $lParam = unpack 'L', pack 'P24', $struct;
        # or
        #$_[2] = unpack 'L', pack 'P24', $struct;
        return 1;
    },
);

##</code><code>##

case WM_MEASUREITEM: 
    lpmis = (LPMEASUREITEMSTRUCT) lParam; 
 
    // Set the height of the list box items. 
 
    lpmis->itemHeight = 30; 
    return true;