use strict;
use warnings;

my $max = 19;

my @aoa = map { [ ( 'o' ) x ($max + 1) ] } 0..$max  ; 

display( @aoa );

# @to_change will contain [row1,col1],[row2,col2]...
my @to_change = illuminate( 5, 4, 6 );

sub illuminate{
	my $center_row = shift;
	my $center_col = shift;
	my $radius     = shift;	
	...
}

sub display{
	foreach my $row ( @_ ){
		foreach my $col ( @$row ){
			print $col;
		}
	print "\n"
	}
}