Hello Mates , can you please Tell what $msg Returns here.

my $maxMsgCodeLength = 15;
my $ip= 192.168.106.60;
my $port= 9000;

sub pStartBEMsg {
  my ($ip, $port) = @_;
  my $msgCode = "StartBE";
  $msgCode = $msgCode.(" " x ($maxMsgCodeLength-length($msgCode)));
  my $msg = pack("a".$maxMsgCodeLength."ia*",$msgCode, $port, $ip);
  return $msg;
}
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I want to know what pack and Unpack do excatly