Re: Regex question - identify which pattern comes first (named captures)

[LanX]

requires 5.10 for named capture groups:

This code will even give you the sequence.

use v5.10;
use strict;
use warnings;

my $str = "AB ABDA DCACCB AAA BSAA CAAB ACS ABA DBA BA DASSABACA A";


while ( $str =~ / (?<_1> BA[ABC]{2} ) | (?<_2> CA[CD]{2} ) | (?<_3> DA
+[SC]{2} ) /gx) {
    print keys %+, " => ", values %+, " at pos ", pos($str), " \n";
}

_2 => CACC at pos 13 
_3 => DASS at pos 48 
_1 => BACA at pos 53

edit

inserted /x for readability

[ikegami]

Adjusted for OP:

if (
   $str =~ /
      (?: (?<_1> BA[ABC]{2} )
      |   (?<_2> CA[CD]{2} )
      |   (?<_3> DA[SC]{2} )
      )
   /x
) {
   my $first = substr( ( keys( %+ ) )[0], 1 );

   ...
}

Update: Added missing ), as LanX pointed out.

[LanX]

You might want to correct this

> (?: