I only started learning Perl 6 within the last week, so please bear with me. :-)

I had a script working nicely, then I added another statement (line D in the code below) and received a run-time error message like this:

The iterator of this Seq is already in use/consumed by another Seq
(you might solve this by adding .cache on usages of the Seq, or
by assigning the Seq into an array)

[download]

From the documentation I gather that I have somehow created a Seq object and then attempted to iterate it a second time. But I don’t understand where or how the Seq object is being created and used.

I managed to pare down the code to the following SSCCE:

use v6;

my @paths = data();
my @dirs.push: $_.split('/') for @paths;    # A
#  @dirs.perl;                              # B
say $_.join('/') for @dirs;                 # C
my $depth = @dirs.map(*.elems).min;         # D

sub data
{
    my $text = q:to/END/;
        /aardvark/bison/camel/dromedary
        /aardvark/bison/camel/dromedary/elephant
        END

    return $text.lines;
}

[download]

Lines A, C, and D are all required to produce the error. Uncommenting line B removes the error (by caching, apparently, although I’m not sure exactly what is cached). So I have 3 questions:

  1. Where are the Seq object(s) being created and used?
  2. I tried examining the contents of @dirs using say @dirs.perl;, but that had the same effect as uncommenting line B. Is there a way to examine the contents of @dirs (like using Data::Dump in Perl5) without introducing changes?
  3. Adding line B removes the error, but feels like a kludge. What is the correct way of writing this sort of code?

In case it matters:

11:03 >perl6 -v
This is Rakudo Star version 2019.03.1 built on MoarVM version 2019.03
implementing Perl 6.d.

12:14 >

[download]

Thanks,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to [Perl6] Seq iterator already consumed by Athanasius

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