c:\@Work\Perl>perl -wMstrict -le
"my $rx = qr/(?^xms:^data_123$)/;
 print $rx;
 ;;
 my $ry = qr/^data_123$/xms;
 print $ry;
 ;;
 my $rz = qr{ T $rx U $ry V }xms;
 print $rz;
"
(?^:(?^xms:^data_123$))
(?^msx:^data_123$)
(?^msx: T (?^:(?^xms:^data_123$)) U (?^msx:^data_123$) V )