A system and method for facilitating packet transformation of multi-protocol, multi-flow, streaming data. Packet portions subject to change are temporarily stored, and acted upon through processing of protocol-dependent instructions, resulting in a protocol-dependent modification of the temporarily stored packet information. Validity tags are associated with different segments of the temporarily-stored packet, where the state of each tag determines whether its corresponding packet segment will form part of the resulting modified packet. Only those packet segments identified as being part of the resulting modified packet are reassembled prior to dispatch of the packet.