#!/usr/bin/env perl6

sub f2( @arr is copy ) {
    my $pos = @arr.end;

        my $value-at-pos = @arr[$pos];
        say "ERR>> value-at-pos = ", $value-at-pos.perl;
        my $new-value = $value-at-pos - 1;
        say "ERR>> new-value = ", $new-value.perl;
}

sub f1( $remains is copy ) {
    my @row = $remains;
    @row = f2( @row );
}

sub MAIN ( Int $n ) {
    f1 $n;
}

ERR>> value-at-pos = 4
ERR>> new-value = 4