#!/bin/bash
s='Verkle trees are shaping up to be an important part of Ethereum'"'"'s upcoming scaling upgrades. They serve the same function as Merkle trees: [you can put a large amount of data into a Verkle tree3], and make a short proof ("witness") of any single piece, or set of pieces, of that data that can be verified by someone who only has the root of the tree.'
sed -E 's/(\[[[:alpha:]]{2}([^][]*[^0-9])?)([0-9]{1,2}])/\1][\3/g' <<< "$s"

IyEvYmluL2Jhc2gKcz0nVmVya2xlIHRyZWVzIGFyZSBzaGFwaW5nIHVwIHRvIGJlIGFuIGltcG9ydGFudCBwYXJ0IG9mIEV0aGVyZXVtJyInIidzIHVwY29taW5nIHNjYWxpbmcgdXBncmFkZXMuIFRoZXkgc2VydmUgdGhlIHNhbWUgZnVuY3Rpb24gYXMgTWVya2xlIHRyZWVzOiBbeW91IGNhbiBwdXQgYSBsYXJnZSBhbW91bnQgb2YgZGF0YSBpbnRvIGEgVmVya2xlIHRyZWUzXSwgYW5kIG1ha2UgYSBzaG9ydCBwcm9vZiAoIndpdG5lc3MiKSBvZiBhbnkgc2luZ2xlIHBpZWNlLCBvciBzZXQgb2YgcGllY2VzLCBvZiB0aGF0IGRhdGEgdGhhdCBjYW4gYmUgdmVyaWZpZWQgYnkgc29tZW9uZSB3aG8gb25seSBoYXMgdGhlIHJvb3Qgb2YgdGhlIHRyZWUuJwpzZWQgLUUgJ3MvKFxbW1s6YWxwaGE6XV17Mn0oW15dW10qW14wLTldKT8pKFswLTldezEsMn1dKS9cMV1bXDMvZycgPDw8ICIkcyI=