perl -e 'print scalar(()=<>),"\n"' filename

##</code><code>##

perl -pe "}{$_=$." filename

##</code><code>##

#!/your/perl/here -p
}{$_=$.

##</code><code>##

#!/your/perl/here
use strict;
use warnings;
while (<>) {}
print "$.\n";

##</code><code>##

#!/your/perl/here
use strict;
use warnings;
my $file_count = @ARGV;
while (<>) {}
continue
{ 
  if (eof)
  {
    # print file names for multiple files
    print "$ARGV: " if ($file_count > 1);
    print "$.\n";
    close ARGV;
  }
}