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Lev, Dex, Identity [.  ].  ]:

[. is a conjunction that yields the left argument and ]. is a conjunction that yields its right argument.

]: is the identity adverb, that yields its argument.                                                                                                

For example:
   sqrt=: %: [. sqr=: *:
   sqrt 1 2 3
1 1.41421 1.73205

   sqr 1 2 3
1 4 9

   ^ ]: 0 1 2 3
1 2.71828 7.38906 20.0855


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