G'day praveensam,

Welcome to the monastery.

I'd recommend the following in the indicated order:

1. perlrequick - Perl regular expressions quick start
2. perlretut - Perl regular expressions tutorial
3. perlre - Perl regular expressions (the rest of the story)
4. Search the perl manual page (for 'regular expression') to find links to other related pages. Be aware, some of these are fairly advanced.