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# [Lua 5.4](https://www.lua.org/versions.html#5.4), 9 bytes

``` lua
n^.5%1==0
```

[Try it online!](https://tio.run/##bY0xCgIxEEVrc4ppJBlYQ1JY5gqyJxCW3YwEZKKzk867x6DY@cv/eP/f29Kp8aqlMpBjBMnahDtf/fkYUwo982bMQwqrsxc7gX3BnIXyqrA/2yLZ4g@f/mZwQ1WgQII4QQwBtmoOX6d8Bq33Wncdzc2RK4hoxm1/Aw)

----

The entire compressed code is 33 bytes:

``` lua
function f(n)return n^.5%1==0 end
```

[Try it here.](https://tio.run/##bY1BDsIgFETXcorZGCBpCSxccgXjCUyaFgyJ@ejvZ@fdsVaXznJe3sy9Tb3nRrOUSsiGLCdpTKCrOx1DjB6Jlv7gQmL0WQ/QL1wS5zQL1mebOGmrfnj8m42rXBkFEWFA8B5LVYevU/ZB7ZzUVbbmZrIp1lr1eX0D)

It's not clear whether the rules allow the first form (i.e. only the relevant expression) or the second form (i.e. the entire piece of code that does the check). I see some use the former, some use the latter.