use strict;
use Spreadsheet::WriteExcel;
my $workbook = Spreadsheet::WriteExcel->new("test.xls");
my $worksheet    = $workbook->add_worksheet();
my $format_heading  = $workbook->add_format();

my $condition = "a";
getFormat($condition);
$worksheet->write("A1", "sometext", $format_heading); 

sub getFormat {
    $condition = shift;
    
    if ($condition eq 'a'){
       $format_heading->set_bg_color('yellow');
    }
    elsif ($condition eq 'b'){
       $format_heading->set_bg_color('pink');
       $format_heading->set_color('red');
    }
    elsif ($condition eq 'c'){
       $format_heading->set_bg_color('blue');
    }
    else {
       $format_heading->set_bg_color('white'); # Default color
    }
}