how do you unpack 3 bytes with perl?

[Greg L]

I need to unpack 3 bytes of data with perl. Normally I would use something like:

my $Operand;
if( $sz_Operand == 1 )
{
$Operand = unpack( 'C', $bBuf );
}
elsif( $sz_Operand == 2 )
{
$Operand = unpack( 'S', $bBuf );
}
elsif( $sz_Operand == 4 )
{
$Operand = unpack( 'L', $bBuf );
}

But what do I use if szOperand is == 3??