use strict;
use warnings;

my @str=qw(ab_xcc3
         ab_xcc3_000
         ok_and
         rajak_acc_idx
         rajak_acs_idx
         BMW_acc
         BMW_asc
         vc_ba
         vc_ba_002
         dc_sts1
         dc_sts6_005);

for(@str) {
   my ($temp)=$_=~/^(\w{2})\_/xi;
   if($temp) {
     ($temp) =$_=~/^(\w{2}\_[a-z0-9]+)/xi;
     print $temp."\n";
   } else {
     ($temp)=$_=~/^([a-z0-9]+)\_/xi;
     print $temp,"\n";
  }
}


__OUTPUT___
ab_xcc3
ab_xcc3
ok_and
rajak
BMW
vc_ba
vc_ba
dc_sts1
dc_sts6