What is the role of the equal sign character in regular expressions when matching XML tags in default-theme?

[piotr-dobrogost]

At #992 (comment) there's a part of default-theme.json shown:

lnav/src/themes/default-theme.json

Lines 207 to 218 in 1ea385e

	"xml": {
	"pattern": "</?([^ >=!]+)[^>]*>",
	"style": {
	"color": "${semantic_highlight_color}"
	}
	},
	"xml-decl": {
	"pattern": "<!([^ >=!]+)[^>]*>",
	"style": {
	"color": "${semantic_highlight_color}"
	}
	}

What is the character = (equal sign) for in the regular expressions there?