$x =min $x, $y; # p5
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For me that's perfect. A function min - thats just three chars, you add = and what you have is the same number of chars (for golfers), much more clear than ?<:=, and more flexible - it can handle lists instead of just pairs.
Update: Sorry this was just just a temporary blurr of my consiousness. It did not address the arguments by BrowserUk.