CSCE 5200 Information Retrieval and Web Search
Spring 2008
Perl warm-up exercises
Note: This assignment is optional, and is meant to help you get started
with Perl. It will not be graded. If you want feedback, you can submit it 
as an email to the instructors by 02/04/2008.



1. Write a program that reads a string from the standard input, and uses a Perl 
regular expression to test whether the string looks like a valid IP address. 
Save the program as validIP.pl.

2. Match the following patterns:
a) an odd digit followed by an even digit (eg. 12 or 74)
b) a letter followed by a non-letter followed by a number
c) a word that starts with an upper case letter
d) the word "yes" in any combination of upper and lower cases letters
e) one or more times the word "the"
f) a date in the form of one or two digits, a dot, one or two digits, a dot, two digits
g) a punctuation mark 
Save your program as regularExpressions.pl

3. Consider the file words.dat 
      the,10000
      where,1000
      a,9999
      an,6000 
The columns represent words and frequencies, as collected from a text collection. 
Write a program that reads in this data, sorts the list of words in descending order 
of their frequencies, and writes them out in the same format, in the file new.dat. 
Save the program as wordOrder.pl

4. Write a program that takes as input an HTML formatted Web page, identifies all the 
URLs that this page links to, and prints them out to the standard output. Your program 
should convert relative URLs into absolute URLs. Save the program as linkExtractor.pl

5. Write a program that reads two files (names are given as command line arguments), 
and prints out a sorted list of all the words in the two files. For each word, prints 
the frequency from file one, file two, and both files. Save your program as 
wordFrequencies.pl

Example: assuming the content of the two files is 
file1: 
the corpus is a collection of conversations in British English
file2: 
the transcripts of the English conversations are also included
output:
British 1 0 1
English 1 1 2
a 1 0 1 
also 0 1 1
are 0 1 1
collection 1 0 1
conversations 1 1 2
corpus 1 0 1
in 1 0 1 
included 0 1 1
is 1 0 1
of 1 1 2
the 1 2 3
transcripts 0 1 1