From @MARTIMM

Hi

I had some discussion on the perl6 users list involving the use of a
List named argument. The example below works correct

perl6 -e 'sub MAIN (List :$dirs=[]) { .say for flat @​$dirs.List».split​:
/","/ }' --dirs=d1 --dirs=d2 --dirs=d3,d4,d5

d1
d2
d3
d4
d5

Giving the --dirs option on command line once however, it shows the
usage message which it shouldn't.

This is Rakudo version 2017.05-338-gaca1929 built on MoarVM version
2017.05-25-g62bc54e implementing Perl 6.c.

Regards
Marcel