use warnings;
use strict;

my @matrix = (
	["A12a1", "img5", "x456", "y456"],
	["A1a2",  "img2", "x123", "y456"],
	["A1a1",  "img1", "x123", "y123"],
	["A10a1", "img4", "x456", "y123"],
	["A1a12", "img3", "x456", "y789"],
);

my @sorted = sort natsort @matrix;
use Data::Dump 'pp';
print pp \@sorted;

sub natsort {
	# sort by first column (note the dereferencing)
	my @a = split /(\d+)/, $a->[0];
	my @b = split /(\d+)/, $b->[0];
	my ($A,$B);
	while (defined($A = shift @a) and defined($B = shift @b)) {
		my $res = ($A =~ /\d/) ? $A <=> $B : $A cmp $B;
		return $res if $res;
	}
	return defined $A ? -1 : 1;
}

__END__

[
  ["A1a1", "img1", "x123", "y123"],
  ["A1a2", "img2", "x123", "y456"],
  ["A1a12", "img3", "x456", "y789"],
  ["A10a1", "img4", "x456", "y123"],
  ["A12a1", "img5", "x456", "y456"],
]