perl: add README (#8215)

plugins/perl/README.md

+# Perl
+
+This plugin adds [perl](https://www.perl.org/) useful aliases/functions.
+
+To use it, add `perl` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... perl)
+```
+
+## Aliases
+
+| Aliases       | Command            |  Description                           |
+| :------------ | :----------------- | :------------------------------------- |
+| pbi           | `perlbrew install` | Install specific perl version          |
+| pbl           | `perlbrew list`    | List all perl version installed        |
+| pbo           | `perlbrew off`     | Go back to the system perl             |
+| pbs           | `perlbrew switch`  | Turn it back on                        |
+| pbu           | `perlbrew use`     | Use specific version of perl           |
+| pd            | `perldoc`          | Show the perl documentation            |
+| ple           | `perl -wlne`       | Use perl like awk/sed                  |
+| latest-perl   | `curl ...`         | Show the latest stable release of Perl |
+
+## Functions
+
+* `newpl`: creates a basic Perl script file and opens it with $EDITOR.
+
+* `pgs`: Perl Global Substitution: `pgs <find_pattern> <replace_pattern> <filename>`
+  Looks for `<find_pattern>` and replaces it with `<replace_pattern>` in `<filename>`.
+
+* `prep`: Perl grep, because 'grep -P' is terrible: `prep <pattern> [<filename>]`
+  Lets you work with pipes or files (if no `<filename>` provided, use stdin).
+
+## Requirements
+
+In order to make this work, you will need to have perl installed.
+More info on the usage and install: https://www.perl.org/get.html