define, like constant, is used at compile-time; hence, it has to be declared before any run. In this case, it really doesn't need to be used, but I used it to for debugging. The result might surprise you.

#!/usr/bin/perl 

use Modern::Perl '2012';
use strictures 1;
no strict 'refs';
use Spreadsheet::ParseExcel;
use Devel::SimpleTrace 'showrefs';
use define DEBUG => 1;

my $parser   = Spreadsheet::ParseExcel->new();
my $workbook = $parser->parse('tags sample.xls');
my $page = $workbook->{Worksheet}[0];

my ( $tags, $pages, $pviews, $pvisits );
format STDOUT_TOP =
Tags        Pages        Page Views        Page Visits
.
format STDOUT = 
@<<<<<<>>>>>>>>> @ >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
$tags, $pages, $pviews,    $pvisits
.

my %i;
foreach ( my $i = 0 ; $i{'MaxRow'} ; ++$i ) {
    $tags    = cell( $page, $i, 0 );
    $pages   = cell( $page, $i, 1 );
    $pviews  = cell( $page, $i, 2 );
    $pvisits = cell( $page, $i, 3 );
    write;
}

cell(DEBUG);

sub cell {
    my ( $Wks, $r, $c ) = @_;
    if ( defined( $$Wks{'Cells'}[$r][$c] ) ) {
        my $val = $$Wks{'Cells'}[$r][$c]->Value;
        chomp $val;
        return $val;
    }
    return '';
}
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