Perl Reference Guide

1. Command Line Options
• -0[octal]
specify record seperator (\0, if no argument)
-a
autosplit mode with -n or -p
-c
check syntax only (runs BEGIN and END blocks)
-d[:debugger]
run scripts under debugger
-D[number/list]
set debuging flags (argument is a bit mask or flags)
-e command
onle line of script, multiple -e options are allowed [filename] can be ommited when -e is used
-F regexp
regular expression for autosplit (-a)
-i
edit <> files in place (make backup if extension supplied)
-l[octal]
enable line ending processing, specifies line terminator
-n
assume 'while(<>){. . .}' loop around your script
-p
assum loop line -n but print line also like sed
-P
run script through C preprocessor before compilation
-s
enable some switch parsing for switches after script name
-S
look for the script using PATH environment variable
-T
turn on tainting checks
-u
dump core after parsing script
-U
allow unsafe operations
-v
print version number and patch level of perl
-V[:variable]
print perl configuration information
-w
turn warnings on for compilation of your script
-x[directory]
strip off text before #!perl line and perhaps cd to directory


2. Literals
• Numeric
  123 123.4 5E9 0xffff(hex) 0377(octal)

  String

  'abc' - literal string, no interpolation occurs

  "abc" - interpolation occurs

  Array

  () - empty array

  (1,2,3) - three element array

  Hash

  (key1,val1,key2,val2,...)


3. Variables
• $var
  A simple scalar variable

  @array

  An array variable

  $array[5]

  The 4th element of an array

  @array[3,4]

  A slice of @array

  %hash

  A hash variable

  $hash{'one'}

  The value of the hash variable with an index of one


4. Operators
• ->
• ++
• --
• **
• \
• ! ~
• + -
• =~
• !~
• * / % x
• + - .
• >> <<
• name unary operators
• < > <= >=
• lt gt l ge
• == != <=>
• eq ne cmp
• &
• | ^
• ||
• .. (range operator)
• ? : (ternary operator)
• = += -= ...
• ,
• =>


5. Statements
• if (expr) block [[elsif (expr) block] else block]
  The if statements

  unless(expr) block [else block]

  The unless statement

  while (expr) block

  The while loop

  until (expr) block

  The until loop

  for([expr];[expr];[expr]) block

  The for loop

  do block while (expr)

  The do-while loop

  do block until (expr)

  The do-until loop

  foreach [var] (list) block

  The foreach loop

  last [label]

  Used immediately exit a loop

  next [label]

  Used to go the next iteration of a loop

  redo [label]

  Used to restart the loop without evaluating the condition


6. Regular Expressions
• .
  Matches any character except a newline unless the \s modifier is used

  ( ... )

  Groups a series of pattern elements to a signle element

  ^

  Matches the beginning of a line

  $

  Marches the end of a line

  [...]

  Sets up a class of characters to match, if [^...] it excludes these.

  |

  Gives you an alternative

  +

  Matches the preceding character one or more times

  ?

  Matches the preceding character zero or one times

  *

  Matches the preceding character zero or more times

  {n,m}

  implies the minimum n and maximum m match count. {n} means exactly n times. {n,} means at least n times.

  \w

  Matches alphanumeric characters

  \s

  Matches whitespace

  \S

  Matches non-whitespace

  \d

  Matches numeric

  \D

  Matches non-numeric

  \b

  Matches word-boundries

  \B

  Matches non-word boundries


7. File Operators
• -r -w -x
  Test if file is readable/writable/executable by user

  -R -W -X

  Test if file is readable/writable/executable by real user

  -o -0

  Test if file is owned by the user/real user

  -e -z

  Test if file exist/has zero size

  -s

  Test if file exist and has a non-zero size. This returns the size.

  -f -d

  Test if file is plain/directory

  -l -S -p

  Test if file is symbolic link/socket/name pipe

  -b -c

  Test if file is a block/character special file

  -u -g -k

  File has setuid/setgid/sticky bit set

  -t

  Test if filehandle is opened to a tty

  -T -B

  Test if file is text/binary

  -M -A -C

  File modification/access/inode-change time.


8. Special Variables
• $_
  The default variable

  $.

  The current input line

  $?

  The status returned by the last `...`command, pipe

  $]

  The Perl version number

  $[

  The index of the first element of an array

  $0

  The name of the file containing the Perl script being executed.

  $$

  Teh process ID of the Perl interpreter running this script

  $@

  The Perl error message from the last eval or do expr command

  $&

  The string matched by the last successful pattern match

  $`

  The string preceding what was matched by teh last succesful match

  $'

  The string followed what was matched by the last successful match.

  $ARGV

  The name of the current file when reading from < >

  @ARGV

  Contains the command line arguments for the script

  @_

  Parameter array for subroutines

  %ENV

  Contains the current environment variable


9. Functions
• chdir
  Changes to specified directory

  chomp

  Removes characters from end of sring corresponding to the input line seperator

  chop

  Removes the last characters

  close

  Closes a filehandlde

  closedir

  Closes a directory opened by opendir()

  defined

  Returns a boolean value depending of whether the variable is defined or not.

  delete

  Use this function to delete an element from a hash given a specified key

  die

  Terminates execution of a perl script

  each

  Allows you loop through a hash, it returns the key and value

  eof

  Test to see if at the end of file

  eval

  Executes a perl expression like a program returning the value of the last statement executed

  exists

  Test if a given key exist in a hash

  exit

  Exits the program with a specified error

  glob

  Returns the list of files resulting from expanding the expression with any wildcards.

  grep(expr,list)

  Evaluates the expression or block for each of the elements supplied in the list

  index

  returns the position in the suplied string where the substring first occurs

  join

  Converts a list into a string with the specified seperator character

  keys

  Returns a list comprising the name of each that exist in a hash

  length

  Returns the length of a string

  open

  Opens a specified file with the specified filehandle

  opendir

  Opens a specified directory

  print

  prints to the specified filehandle

  push

  Appends elements to the specified list

  readdir

  Returns a list of files specified by the directory handle

  shift

  Takes the left most element from an array and returns that

  split

  Takes a string and splits it into a list based of the specified expression

  unshift

  Inserts an element into the beginning of a list

  values

  Returns the values that exist in a hash