update: You can use "$." for counting lines.

my $i =0;
open (FILE, "myfile.txt");
while (<FILE>)
{
++$i;
if($. == 10)
{
    print $_;
    print "\n Reached\n"
}
}
print $i;#will print number of lines in the file
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You can use an array to store the file and use scalar @arr to get the array size.