Answer by Vivian De Smedt for How to validate and reference digraph /special character in Vim?

The special character ^[ is actually Esc.

If you want to include it in a regex you can type it using the following key sequence:

Ctrl vEsc

In general in presence of a special character you can discover its code using the ga command. Move the cursor on the character and hit ga.

The output gives you:

• The decimal code (27 in case of Esc)
• The hexadecimal code (1b in case of Esc)
• The digraph if any (EC in case of Esc)

You can use that information to reinsert the same character in insert mode:

• Ctrl v027
• Ctrl vx1b
• Ctrl kEC