Understadning Perl Basics

my $file = <STDIN>;
open(READFILE, "$file") || die "No File Found";

if ($file !~ m/.txt$/)
{
$file .= ".txt";
} else {
print "There was already a .txt filename\n";
}

my $i = 0;
while (<READFILE>)
{
$i++;
}
print ("There are " . $i . " Lines in " . $file);
close(READFILE);

my $lin = "Lines: \n";
chomp($lin);
enter:
{
print("Please enter a file name: ");
$fileName = <STDIN>;
chomp($fileName);
 
if($fileName !~ m/\.TXT$/i)
 {
  open(READFILE, "$fileName.txt") || die "couldn't open file: $!";
        }
else
 {
 print("re-enter filename!\n");
 redo enter;
}
}
while(<READFILE>)
{
package Lines;
 $count += split(/\n\n/, $_);
}
print("$lin $Lines::count\n");
close(READFILE);

my ($lastchar,$lines,$file,$paragraphs,$ch);
print("enter filename: ");
my $file = <STDIN>;
chomp($file);
if ($file !~ m/\.txt$/)
{
$file .= ".txt";
} 
open(READFILE, "$file") || die "No File Found";
my $i = 1;
while ($ch = getc(READFILE))
{
if ($ch eq "\n") # if newline...
 {
  $lines++; # count another line
  if ($lastchar eq "\n") # if last character also newline
  {
  $paragraphs++; # count another paragraph
  }
 }
}
print ("There are " . $i . " Lines in " . $file);
close(READFILE);