use strict;
use warnings;

my $size = 24 * 1024 * 1024;
my ( $numlines, $occurances ) = ( 0, 0 );

open my $fh, '<', '/home/mario/Dictionary2GB.txt' or die "$!";

while ( read( $fh, my $b, $size ) ) {
   $b .= <$fh> unless ( eof $fh );
   $numlines   += $b =~ tr/\n//;
   $occurances += () = $b =~ /123456\r?$/mg;
}

close $fh;

print "Num lines : $numlines\n";
print "Occurances: $occurances\n";