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# [Ruby], 15 bytes

```ruby
->a{a.all?a[0]}

->a{          }  # lambda taking array `a`
    a.all?       # do all items in the array match... 
          a[0]   # ...the first? 
```

[Try it online!][TIO-ktambyyg]

[Ruby]: https://www.ruby-lang.org/
[TIO-ktambyyg]: https://tio.run/##KypNqvyfZvtf1y6xOlEvMSfHPjHaILb2f0FpSbFCmp5GtKEOFMZqcsEFDcBCZjrmyIIoKmI1/wMA "Ruby – Try It Online"