my $re = qr{
  (?>      # don't backtrack into this group
     !.    # either the escape character,
           # followed by any other character
     |     # or
     [^!;\n] # a character that is neither escape
           # nor split character
  )+
}x;

while ($str =~ /($re)/g) {
   print "Chunk '$1'\n";
}