how to extract Operator like "<="

[xixiliguo]

Below is my code

package main

import (
	"fmt"

	"github.com/alecthomas/participle/v2"
)

type Field struct {
	Name     string `@Ident`
	Operator string `@(">=" | ">" | "<=" | "<" | "==" | "!=")`
	Value    int    `@Int`
}

func main() {
	parser, err := participle.Build[Field]()
	fmt.Printf("%s %s\n", parser, err)
	ast, err := parser.ParseString("", `a <= 123`)
	fmt.Printf("%+v %+v\n", ast, err)
}

It output error "unexpected token "=" (expected )", can someone tell why ?
I found if change a <= 123 to a < 123, code can work well, it seems parser for Operator only extract single chracater ?

Field = <ident> (">=" | ">" | "<=" | "<" | "==" | "!=") <int> . %!s(<nil>)
&{Name:a Operator:< Value:0} 1:4: unexpected token "=" (expected <int>)

[alecthomas]

The default lexer has separate tokens for < and = so you'll need to match them separately, or write your own lexer.