Documentation for method outer-caller-idx assembled from the following pages:

Class: Backtrace §

From Backtrace

(Backtrace) method outer-caller-idx §

Defined as:

method outer-caller-idx(Backtrace:D: Int $startidx)

Returns as a list the index of the frames that called the current one.

sub zipi { { { die "Something bad happened" }() }() };
try zipi;
say $!.backtrace.outer-caller-idx( 4 ); # OUTPUT: «[6]␤»