man  Linux manual pages
perldoc  Perl Programmers Reference Guide
info  Info documents - Documentation browsing system
apropos  Search the Whatis database for strings

1 - General Commands 		intro(1)
2 - System Calls 		intro(2)
3 - Subroutines 		intro(3)
4 - Special Files 		intro(4)
5 - File Formats 		intro(5)
6 - Games 			intro(6)
7 - Macros and Conventions 	intro(7)
8 - Maintenance Commands 	intro(8)
9 - Kernel Interface 		intro(9)
n - New Commands