Proposed BIP for OP_CAT

The email discusses the topic of script size limits in Bitcoin. The sender mentions that without a limit of 520 bytes, it is possible to construct a script using various operations. They provide an example of a script that repeats a string multiple times on the stack and performs other operations like SHA256SUM. By doing so, the maximum memory required to verify a single script can be increased from around 520kB to approximately 10MB.

The sender also mentions that the 10kB limit applies to scriptPubKey, scriptSig, and segwit v0 scripts. They point out that there are examples of larger tapscripts, such as the ones provided in the links: one with 3,938,182 bytes of script (which is non-standard due to being an oversized transaction) and another with 360,543 bytes of script (which is standard).

In conclusion, the email highlights the possibility of constructing larger scripts by bypassing the 520-byte limit and provides examples of such scripts.