From @AlexDaniel

You can put any negative number (even -Inf) and it will not die​:

<AlexDaniel> m​: say 'foo foo foo'.subst(/foo/, "bar", :nth(-Inf));
<camelia> rakudo-moar ab73b0​: OUTPUT«foo foo foo␤»

However, from https://github.com/rakudo/rakudo/blob/nom/src/core/Str.pm#L606
:
fail "Attempt to retrieve negative match :nth($n)" if $n < 1;

So it seems like it does not work?

Also, it should talk about allowing only positive values because the
conditional is checking for < 1.

From @usev6

This seems to work now​:

$ perl6 -e 'say "foo foo foo".subst(/foo/, "bar", :nth(-Inf));'
Attempt to retrieve before :1st match -- :nth(-Inf)
  in block <unit> at -e​:1

skids++ added tests with commit e502eaf9.

For some reason a few of those tests still fail (do not die) on rakudo.jvm.

I'll flag this ticket as [JVM] and use it to fudge those failing tests.

@usev6 - Status changed from 'new' to 'open'

From @usev6

The failing tests on JVM behave correctly, when executed on the command line​:

$ perl6-j -e 'my $data = "f fo foo fooo foooo fooooo foooooo"; $data ~~ m​:nth(-1)/fo+/; say "alive"'
Attempt to retrieve before :1st match -- :nth(-1)
  in block <unit> at -e​:1

The same code in the test file (using 'throws-like') does not die. So, maybe the problem is somewhere else.

From @usev6

All the tests fudged with this ticket number are passing now​: Raku/roast@8d39a9b

I'm closing this ticket as 'resolved'.

@usev6 - Status changed from 'open' to 'resolved'