$grammar = q{
start: seq

seq: '(' seqstr(s) ')'

seqstr: seq | tagstr

tagstr: OZN ( seq | rijec )

OZN: /[A-Z.,?'*:`*]+ /
rijec: /[\w-?,:<*`*]+/
};

##</code><code>##

use Grammar::BNF;
my $g = Grammar::BNF.generate(Q:to<END>
<start> => <seq>

<seq> => '(' <seqstr(s)> ')'

<seqstr> => <seq> | <tagstr>

<tagstr> => <OZN> '(' <seq> | <rijec> ')'

<OZN> => /[A-Z.,?'*:`*]+ /
<rijec> => /[\w-?,:<*`*]+/
END
);