>perl -le '$s="1:05:02.599,xx:MTV = 0x2f7c:COOL_CALL, an option = 11"; 
(undef, $s) = unpack "a21 a6", $s; print $s'
0x2f7c
>perl -le '$s="1:05:02.599,xx:MTV = 0x2f7c:COOL_CALL, an option = 11"; 
$i=index $s, ":COOL_CALL"; print substr $s, $i-6, 6'
0x2f7c