Is the input given by the user a number? (BTW which one is a number: 23, 2.3, 2.3.4, 2.4e3, abc ?) Is there a word in the file that is repeated 3 or more times? Replaces all occurrences of Perl or perl by Java ... ... but avoid replacing Perla. Given a text message fetch all the phone numbers: Fetch numbers that look like 09-1234567 then also fetch +972-2-1234567 and maybe also 09-123-4567 Check if in a given text passing your network there are credit card numbers.... Given a text find if the word "password" is in it and fetch the surrounding text. Given a log file like this: [Tue Jun 12 00:01:00 2006] - (3423) - INFO - ERROR log restarted [Tue Jun 12 09:08:17 2006] - (3423) - INFO - System starts to work [Tue Jun 13 08:07:16 2006] - (3423) - ERROR - Something is wrong provide statistics on how many of the different levels of log messages were seen. Separate the log messages into files.