From zefram@fysh.org

With [perl #​126897] fixed, deparsing of some kinds of structure containing
Slip objects now runs into the interpolation of Slip objects into lists.
This leads to round-trip failures​:

my @​a = (11,22,33)
[11 22 33]
@​a[1] := slip(44,55)
(44 55)
@​a.perl
[11, slip(44, 55), 33]
@​a.perl.EVAL.perl
[11, 44, 55, 33]
@​a.List.perl
(11, slip(44, 55), 33)
@​a.List.perl.EVAL.perl
(11, 44, 55, 33)
@​a.Slip.perl
slip(11, slip(44, 55), 33)
@​a.Slip.perl.EVAL.perl
slip(11, 44, 55, 33)

The deparsing needs to take account of the interpolation, and produce
output that either avoids it or corrects for it. Before [perl #​126897],
of course, round-tripping of these structures failed in the more obvious
manner of turning the Slip into a List.

-zefram