my @vector = (4.3125, 0.4375);
push @AoA, @vector;
@vector = (4.375, 0.375);
push @AoA, @vector;
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(4.3125, 0.4375, 4.375, 0.375)
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my @vector = (4.3125, 0.4375);
push @AoA, \@vector;
@vector = (4.375, 0.375);
push @AoA, \@vector;
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push @AoA, [4.3125, 0.4375];
push @AoA, [4.375, 0.375];
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As I said earlier, you should avoid using the $a and $b variables, they are special variables used among other things for sorting, they behave differently from other variables, and using as you do them might lead to difficult-to-track bugs. You may use $c or $d, if you like, this will not be a problem, but I would personally put a more meaningful name helping comprehension of what they represent.

Update: As pointed below by farang the first method above for building an AoA is actually buggy. Use the second one. Thanks to farang for picking that.

You need to push on @AoA a reference to @vector:

my @vector = (4.3125, 0.4375);
push @AoA, \@vector;
@vector = (4.375, 0.375);
push @AoA, \@vector;
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That way is buggy, though, as the redefinition of @vector will clobber the first pushed array element. This is explained under COMMON MISTAKES in perldsc, "taking a reference to the same memory location repeatedly".

So both lines above should instead use a square bracket reference.

push @AoA, [ @vector ];
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You are right, it's a mistake to push references to the same array without declaring it anew. I have been bitten by that a couple of times, I should know better. That's why I am actually almost always using the second method using the [] anonymous array reference constructor.

$ perl sill2.pl
elt 0 0 is 0.4375
elt 0 1 is 4.3125
elt 0 2 is bath-left
elt 1 0 is 0.375
elt 1 1 is 4.375
elt 1 2 is bath-middle
elt 2 0 is 0.375
elt 2 1 is 4.4375
elt 2 2 is bath-right
bath-left has slope 5.82263230478133
bath-middle has slope 4.91710033552881
bath-right has slope 4.84767847916148
$ cat sill2.pl
#!/usr/bin/perl -w
use strict;
use 5.010;
use Math::Trig;
BEGIN { push @INC, ".."; }
use utils1;

my @AoA;
my $aoa_ref = \@AoA;
my $vector_ref = [0.4375, 4.3125, "bath-left"];
push @AoA, $vector_ref;
$vector_ref = [0.375, 4.375,  "bath-middle"];
push @AoA, $vector_ref;
$vector_ref = [0.375,4.4375, "bath-right"];
push @AoA, $vector_ref;
print_aoa($aoa_ref);
for my $i ( 0 .. $#AoA ) {
   my $ratio = $AoA[$i][0]/$AoA[$i][1];
   my $rad = asin($ratio);
   my $degrees  = rad2deg($rad);
   my $name = $AoA[$i][2];
   say "$name has slope $degrees";
   }
__END__ 
$
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This might be the most robust version of this material.

$ cd ..
$ pwd 
/home/fred/Desktop/root3/pages/sills/template_stuff
$ ls
aimages          config1.pm               lime1.css     pm4.txt
basketball1.css  football1.pm             mango1.css    rebus1.tmpl
bathfan1.css     football2.pm             marvin1.css   rebus2.tmpl
blue1.css        footer_center2.txt       math1.pm      rebus3.tmpl
bom              footer_center_begin.txt  nibley1.pm    rebus4.tmpl
bottom1.txt      footer_center.txt        oibottom.txt  rory1.css
captions         giles1.css               oitop.txt     ruscaptions
ceres1.css       hc_input2.txt            pears1.css    sills1.css
code1.tmpl       hc_input.txt             plum1.css     utils1.pm
code2.tmpl       html1.pm                 pluto1.css    utils1.pm~
code3.tmpl       lemon1.css               pm1.txt       watermelon1.cs
+s
$ cat utils1.pm
package utils1;
require Exporter;
use config1;

our @ISA = qw(Exporter);
our @EXPORT = qw( invert_aoa print_hash print_aoa
highest_number get_list zip_lists p_tag);

sub invert_aoa{
use strict;
use warnings;
use 5.010;

my $a = shift;
my @AoA = @$a;
my $k = $#AoA;
#say "k is $k"; 
my @BoB;
    for my $i ( 0 .. $#AoA ) {
        my $aref = $AoA[$i];
        my $x = $#{$aref};
        #say "x is $x";
        for my $j ( 0 .. $#{$aref} ) {
            $BoB[$j][$i]= $AoA[$i][$j];
        }
    }
my $b = \@BoB;
return $b;
}
sub print_aoa{
use strict;
use warnings;
use 5.010;

my $a = shift;
my @AoA = @$a;
    for my $i ( 0 .. $#AoA ) {
        my $aref = $AoA[$i];
        for my $j ( 0 .. $#{$aref} ) {
            print "elt $i $j is $AoA[$i][$j]\n";
        }
    }
return $a;
}

sub highest_number{
use strict;
use File::Basename;
use Cwd;

my ($aref, $filetype, $word) = @_;
my $number;
my @matching;
my $ext = ".".$filetype;
push (@matching, 0); #min returned value
for my $file (@{$aref}) {
#print "file is $file\n";
if ($file =~ /^$word(\d*)$ext$/){
   #print "matching is $file\n";
   push (@matching, $1);
   }
}
@matching = sort @matching;
my $winner  = pop @matching;
return $winner  
}

sub print_hash{
   my $hash_ref = shift;
   print "subroutine says this is your hash: \n";
   my %hash = %$hash_ref;
   while ( (my $key,my $value) = each %hash )
   {
      print "key: $key, value: $hash{$key}\n";
   }
}

sub get_list{
use strict;
use warnings;
use 5.010;
use File::Slurp;

my $file = shift;
my @lines = read_file($file);
chomp(@lines); 
s/^\s+|\s+$//g for @lines;
@lines = grep length, @lines;
return @lines;
}

sub zip_lists  {
use strict;
use warnings;
use 5.010;
use List::MoreUtils qw( zip );

my ($file1, $file2) = @_;
my @file1lines = get_list($file1);
my @file2lines = get_list($file2);
say "keys are @file1lines";
say "values are @file2lines";
my %hash = zip @file1lines, @file2lines;
return \%hash;
}

sub p_tag  {
use strict;
use warnings;

my $text = shift;
my $before = '<p>';
my $after = '</p>';
my $return = $before.$text.$after;
return \$return;
}

1;

$
[download]

What I found when field measuring was that it was much more attainable to get hypotenuses and heights, so that left me looking for arcsin. I had hoped to get this processed as an AoA, but I'm not quite there yet....

$ perl slope8.pl
bath-left
theta is 5.82263230478133
bath-middle
theta is 4.91710033552881
bath-right
theta is 4.84767847916148
dining-south
theta is 15.2575232904564
john-north
theta is 16.0133944239485
middle-front
theta is 24.6243183521641
south-front
theta is 14.4775121859299
$ cat slope8.pl
#!/usr/bin/perl -w
use strict;
use 5.010;
use Math::Trig;
BEGIN { push @INC, ".."; }
use utils1;

my @AoA;
my $aoa_ref = \@AoA;

my $tja = 0.4375/4.3125;
say "bath-left";
my $hja = asin $tja;
my $degrees  = rad2deg($hja);
say "theta is $degrees";

$tja = 0.375/4.375;
$hja = asin $tja;
say "bath-middle";
$degrees  = rad2deg($hja);
say "theta is $degrees";

say "bath-right";
$tja = 0.375/4.4375;
$hja = asin $tja;
$degrees  = rad2deg($hja);
say "theta is $degrees";

say "dining-south";
$tja = 1.25/4.75;
$hja = asin $tja;
$degrees  = rad2deg($hja);
say "theta is $degrees";

say "john-north";
$tja = 1.0/3.625;
$hja = asin $tja;
$degrees  = rad2deg($hja);
say "theta is $degrees";

say "middle-front";
$tja = 1.875/4.5;
$hja = asin $tja;
$degrees  = rad2deg($hja);
say "theta is $degrees";

say "south-front";
$tja = 1.125/4.5;
$hja = asin $tja;
$degrees  = rad2deg($hja);
say "theta is $degrees";
__END__ 
$
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