use warnings;
use strict;

my $datamat =
  "He said, »Someone once said ›This is what they said‹ but I say something else.«";
print qq{'$datamat' \n\n};

my $i = 0;

$datamat =~ s{ » (.*?) « }
             { ++$i;  qq{<q marker="»" sID="$i"/>$1<q marker="«" eID="$i"/>}; }xmsge;

$datamat =~ s{ › (.*?) ‹ }
             { ++$i;  qq{<q marker="›" sID="$i"/>$1<q marker="‹" eID="$i"/>}; }xmsge;

print qq{[[$datamat]] \n\n};