package L;
use warnings;
use strict;
use File::Slurp;

sub include {
    my ($f) = @_;

    eval {
        my $e = eval qq(#line 1 "$f"\n) . read_file $f;
        die $@ if $@;
    };

    if ($@) {
        die $@
            if ref($@) ne '' or $@ =~ /stack trace:/s;

        my $max_depth = 30;
        my $err       = "error loading '$f': $@stack trace:\n";
        my $e         = -1;
        my @stack;
        my $i;
        for ($i = 0 ; $i < $max_depth ; ++$i) {
            my ($package, $filename, $line, $subroutine) = caller($i);
            last unless $package;

            # removing two evals below every include
            splice(@stack, -2, 2)
                if @stack > 2 and $subroutine eq "L::include";

            push(@stack, "   $subroutine called at $filename line $line");
        }
        $err .= join("\n", @stack, "");
        $err .= "...\n"
            if $i == $max_depth;
        die $err;
    }
}

1;