#!/usr/bin/perl

use warnings;
use strict;
use diagnostics;
use Data::Dumper;

sub left_triangle {
	my @ali=@_;
	my @aoa2;
	foreach (1..@ali-1) {
		pop @{$ali[$_]}; 	
		#push @aoa2, $ali[$_];
	}
	return \@ali;
}

my @xx = ([3],[7,5],[2,4,6],[8,5,9,3]);
print Dumper left_triangle(@xx);
print Dumper \@xx;