Can I limit each color component to 1?

I have a very simple additive shader. I have noticed that if I place quads using this shader on top of each other, and if the textures of the two quads combine on a pixel where the color adds up such that the resulting color components of that pixel are greater than one, the color (white) seems to bleed onto other pixels. Sometimes I can handle this by dimming the texture of one or both quads, but I would really like to be able to put logic into my shader that limits the result color to 1 for all components. Can this be done?

Here is the current shader:

Shader "Custom/AdditiveTexture" 
{

	Properties 
	{
		_Color ("Main Color", Color) = (1,0.5,0.5,1)
		_MainTex ("Texture", 2D) = ""
	}

	SubShader 
	{ 
		Tags {Queue = Transparent} Blend One One ZWrite Off 
		Pass 
		{ 
			SetTexture[_MainTex] 
			{
				// Sets our color as the 'constant' variable
				constantColor [_Color]
                
                // Multiplies color (in constant) with texture
                combine constant * texture
			}
		}
	}
}

There is a clamp function for shaders, but I don’t know if it works with the Fixed Function syntax that you’re using.