c:\@Work\Perl>perl -wMstrict -le
"my $rx = qr/^data_123$/i;
 print $rx;
 ;;
 for my $s (qw(data_123 DATA_123 dAtA_123  data_123x data_12 nada_123)) {
   if ($s =~ $rx) {
     print qq{'exact' match to '$s'};
     }
   else {
     print qq{NO match to '$s'};
     }
   }
"
(?^i:^data_123$)
'exact' match to 'data_123'
'exact' match to 'DATA_123'
'exact' match to 'dAtA_123'
NO match to 'data_123x'
NO match to 'data_12'
NO match to 'nada_123'