($): variable is a name for a container that holds one or more values; use $ to get the value.

(!): negation operator

(tr/): transliterating one group of characters into another. * (s/): substitution

(%): modulus operator:

/s : match any character with

! : negation operator and see P35

\s : shortcut for whitespace

\s+ : match for one or more whitespace characters

\S+ : match any character that their counterpart would not match

/g : global replacements

-p option : tells perl to write a program for you/file is a named pipe

-e option : executable code follow / file or directory name exist

/d : modifier delete found but unreplaced characters

(=~): right against string on the left

== : equal

= : assignment operator

. : string values can be concatenated with the . operator

( * ): match the preceding item 0 or more times

m : pattern match operator * ^ : carets * mkdir : make a directory * GetOptions: the option name is followed by an = (means this option requires a value and s. * grep operator: picking some items from a list can be done with grep * grep command: which print out text lines matching a given pattern. * (whitespace): characters like space, tabs, and newlines. * (\d, \w, \s): nondigital characters, nonword character,,or a nonwhitespace characters. * (\D, \W, \S): match any character that their counterpart would not match