I use airodump-ng to obtain the .cap file, I was trying to know if it is possible to analyze the .cap file if there's an wpa handshake using perl and if it is possible to decrypt the .cap file. Thanks for reply
A cursory Google search for airodump-ng capture file format shows this tutorial, where Wireshark is used to display and analyze a capture file. This means that libpcap can read the capture files. So maybe now it's time to revisit your failed attempts with Net::PCap and try again?