Analysing text files to obtain statistics on their content

You are to write a Perl program that analyses text files to obtain statistics on their content. The program should operate as follows:

1) When run, the program should check if an argument has been provided. If not, the program should prompt for, and accept input of, a filename from the keyboard.

2) The filename, either passed as an argument or input from the keyboard, should be checked to ensure it is in MS-DOS format. The filename part should be no longer than 8 characters and must begin with a letter or underscore character followed by up to 7 letters, digits or underscore characters. The file extension should be optional, but if given is should be ".TXT" (upper- or lowercase).

If no extension if given, ".TXT" should be added to the end of the filename. So, for example, if "testfile" is input as the filename, this should become "testfile.TXT". If "input.txt" is entered, this should remain unchanged.

3) If the filename provided is not of the correct format, the program should display a suitable error message and end at this point.

4) The program should then check to see if the file exists using the filename provided. If the file does not exist, a suitable error message should be displayed and the program should end at this point.

5) Next, if the file exists but the file is empty, again a suitable error message should be displayed and the program should end.

6) The file should be read and checked to display crude statistics on the number of characters, words, lines, sentences and paragraphs that are within the file.



I am very new to Perl and have managed to compile this code using examples from various books. Could anyone oversee this coding and see how it could be improved.
Code:
#!/usr/bin/perl 

use strict; 
use warnings; 

if ($#ARGV == -1) #no filename provided as a command line argument. 
{ 
print("Please enter a filename: "); 
$filename = <STDIN>; 
chomp($filename); 
} 
else #got a filename as an argument. 
{ 
$filename = $ARGV[0]; 
} 

#perform the specified checks 
#check if filename is valid, exit if not 
if ($filename !~ m^/[a-z]{1,7}\.TXT$/i) 
{ 
die("File format not valid\n");) 
} 

if ($filename !~ m/\.TXT$/i) 
{ 
$filename .= ".TXT"; 
} 

#check if filename is actual file, exit if it is. 
if (-e $filename) 
{ 
die("File does not exist\n"); 
} 

#check if filename is empty, exit if it is. 
if (-s $filename) 
{ 
die("File is empty\n"); 
} 

my $i = 0; 
my $p = 1; 
my $words = 0; 
my $chars = 0; 

open(READFILE, "<$data1.txt") or die "Can't open file '$filename: $!"; 

#then use a while loop and series of if statements similar to the following 
while (<READFILE>) { 
chomp; #removes the input record Separator 
$i = $.; #"$". is the input record line numbers, $i++ will also work 
$p++ if (m/^$/); #count paragraphs 
$my @t = split (/\s+/); #split sentences into "words" 
$words += @t; #add count to $words 
$chars += tr/ //c; #tr/ //c count all characters except spaces and add to $chars 
} 


#display results 
print "There are $i lines in $data1\n"; 
print "There are $p Paragraphs in $data1\n"; 
print "There are $words in $data1\n"; 
print "There are $chars in $data1\n"; 

close(READFILE);

Last edited by shabbir; 26Jun2008 at 08:02.. Reason: Code block