use strict;
use warnings;

my ( $length, @lengths );
my $last = 0;

while ( <DATA> ) {
  next unless /Z\s+(\d+)\s+(\d+)/ and $2 >= $1;
  if ( $1 > $last + 1 ) {
    push @lengths, $length if $length;
    $length = $2 - $1 + 1;
  }
  else {
    $length += $2 - $1 + 1;
  }
  $last = $2;
}
push @lengths, $length;

print scalar @lengths, " Z items found:\n";
print join "\n", @lengths;

__DATA__
Z    1   1
Z    5  89
~#à^''$%!@ => line noise

Z   91 102
Z  103 123
Z  124 150
Z  151 191
Z  500 504
Z  505 509