committable6

query

(-> @a[3] { dd MY::.keys })(my @b[3] = <a b c>)

result

¦«2015.12,2016.01.1,2016.02,2016.03,2016.04,2016.05,2016.06,2016.07.1,
  2016.08.1,2016.09,2016.10,2016.11,2016.12,2017.01,2017.02,2018.11»:
("\$_", "\$*DISPATCHER", "\@a[3]").Seq

¦«2017.03,2017.04.3,2017.05,2017.06,2017.07,2017.08,2017.09,2017.10,
  2017.11,2017.12,2018.01,2018.02.1,2018.03,2018.04.1,2018.05»:
("\$_", "\@a[3]", "\$*DISPATCHER").Seq

¦«2018.06»:
("\$*DISPATCHER", "\@a[3]", "\$_").Seq

¦«2018.08,2018.12»:
("\@a[3]", "\$*DISPATCHER", "\$_").Seq

¦«2018.09»:
("\$*DISPATCHER", "\$_", "\@a[3]").Seq

¦«2018.10,2019.03.1,2019.07.1,HEAD(ed8f514)»:
("\@a[3]", "\$_", "\$*DISPATCHER").Seq