This is a small snippet.

Create this function in your shell:

# .bashrc / .zshrc

camelcase() {
    perl -pe 's#(_|^)(.)#\u$2#g'
}

If you use fish:

# .config/fish/config.fish

function camelcase
    perl -pe 's#(_|^)(.)#\u$2#g'
end

Then, you can convert standard input to CamelCase:

~> echo array_map | camelcase
ArrayMap

These functions are useful themselves. Furthermore, you can use them in Vim.

Select snake_case lines to be converted, then type !camelcase then press return key.

Appendix

You can convert CamelCase to snake_case with this function:

function snakecase
    perl -pe 's#([A-Z])#_\L$1#g' | perl -pe 's#^_##'
end

We can enhance vim using command line function.
Hope this article helps you have a better CUI experience in Vim.