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My system doesn't have `perl` in $PATH, so using this theme clutters the
shell output quite a bit.

Turns out, the same thing can be accomplished in pure zsh (with
extendedglob).
Co-Authored-By: Marc Cornellà <marc.cornella@live.com>

Fixes #2317
Closes #2321

Use add-zsh-hook to add functions to hooks. That way they won't be added again
when doing `source ~/.zshrc` multiple times.
Co-authored-by: Marc Cornellà <marc.cornella@live.com>

Fix "command not found: add-zsh-hook" since #3053 removes `autoload -U add-zsh-hook`

if the length of the prompt (excluding color escapes) exceeds 40
characters, emit the arrow prompt on its own line

This helps a lot on smaller terminals