c:\@Work\Perl>perl -wMstrict -le
"my $s = qq{xxx \@B grab \n this \@E yy zzzz \@B and \n this \n too \@E qq};
 print qq{[[$s]]};
 ;;
 my @captures = $s =~ m{ \@B .*? \@E }xmsg;
 print qq{<<$_>>} for @captures;
"
[[xxx @B grab
 this @E yy zzzz @B and
 this
 too @E qq]]
<<@B grab
 this @E>>
<<@B and
 this
 too @E>>

##</code><code>##

c:\@Work\Perl>perl -wMstrict -le
"my $s = qq{xxx \@B grab \n this \@E yy zzzz};
 print qq{[[$s]]};
 ;;
 my @captures = $s =~ m{ \@B (.*?) \@E }xmsg;
 print qq{<<$_>>} for @captures;
"
[[xxx @B grab
 this @E yy zzzz]]
<< grab
 this >>