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Perl Quick Reference

($): 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
( ^ ): the caret match the beginning of a line
$ : match the end of a line or m
~ : p169 of learning perl
cd .. : home directory
head : output the first part of the file
perl : practical extraction
p74 drwxrwxr-x: file type (d):dir, (L):symbolic link,
chmod: (p80 - 81)
(u,g,o): user, group, other
(r,w,x): read, write, excute