set_border(), set_top(), etc are FORMAT methods not WORKSHEET or WORKBOOK methods. 
#!perl
use strict;
use Excel::Writer::XLSX;

my $workbook = Excel::Writer::XLSX->new( 'borders.xlsx' );
my $worksheet = $workbook->add_worksheet();

my $fmt_top = $workbook->add_format();
$fmt_top->set_top();

$worksheet->set_column( 'A:B', 30, $fmt_top );

[download]
see Excel::Writer::XLSX
poj

In reply to Re^3: Adding Borders to Cells using Excel::Writer::XLSX by poj
in thread Adding Borders to Cells using Excel::Writer::XLSX by GuiPerl

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