From @zoffixznet

Works (space between brackets and <a>)​:

  $ perl6 -e 'dd [[ <a>],]'
  [["a"],]

Doesn't (no space)​:

  $ perl6 -e 'dd [[<a>],]'
  ===SORRY!=== Error while compiling -e
  Unable to parse expression in bracketed infix; couldn't find final ']'
  at -e​:1
  ------> dd [[<⏏a>],]

From @zoffixznet

On Tue, 04 Jul 2017 09​:20​:18 -0700, cpan@​zoffix.com wrote​:

Works (space between brackets and <a>)​:

$ perl6 \-e 'dd \[\[ \<a>\],\]'
\[\["a"\],\]

Doesn't (no space)​:

$ perl6 \-e 'dd \[\[\<a>\],\]'
===SORRY\!=== Error while compiling \-e
Unable to parse expression in bracketed infix; couldn't find final '\]' 
at \-e&#8203;:1
\-\-\-\-\-\-> dd \[\[\<⏏a>\],\]

This isn't a bug but By Design. There's a formal ambiguity between Array constructors and reductions, and the way to resolve them is to use a space​:

https://irclog.perlgeek.de/perl6-dev/2017-07-05#i_14830532

@zoffixznet - Status changed from 'new' to 'rejected'