What's the plugin equivalent for THIS_SCRIPT?

[BirdOPrey5]

I have a plugin, I only want code to execute if the page being displayed is a specific page... say showthread....

In a template I'd use:
<if condition="THIS_SCRIPT == 'showthread'">
blah blah blah
</if>

but in a plugin :
if {THIS_SCRIPT == "showthread")
{
blah blah blah
}
doesn't work... is their an equivalent condition I can use in a plugin to see what script I'm in.

I understand I could use a hook location native to the script I want to use but for various reasons that is not an option.