Covert data in excelsheet in bold without using spreadsheet::writesheet

[nickyspace]

Hi

I have a little issue with the exchelsheet .
I have converted data into excelsheet sucessfully .But now i want to make Column Heading Bold . I have searched a lot in google but i havent got any solution. Due to the module is not present, i havent used spreadsheet::writeexcel.

So anyone here in this forum can provide me the solution for this.Below is the Column heading and want to convert into bold .

$exl1 .="ZONE_CODE"."\t"."DISTRIBUTOR_NAME"."\t"."CATEGORY"."\t"."ACTIVE_STATUS"."\t"."NEW_CODE"."\t"."OPERATOR_NAME"."\t"."O
P_STATUS"."\t"."NO_OF_SUBS"."\t"."CONTRACT_RATE"."\t"."FIX_AMOUNT"."\t"."PRODUCT_CODE"."\t"."PROD_DESC"."\t"."TOTAL_CHANNELS"
."\t"."SCHEME_NAME"."\n";

print $exl1."\n";

Please reply if anyone can help me out.