Conventions

Command-Line Options

-a

turns on autosplit mode when used with -n or -p. Splits to @F.

-c

checks syntax but does not execute.

-d

runs the script under the debugger. Use -de 0 to start the debugger without a script

-D NUMBER

sets debugging flags.

-e COMMANDLINE

may be used to enter a single line of script. Multiple -e commands may be given to build up a multiline script.

-F REGEXP

specifies a regular expression to split on if -a is in effect.

-iEXT

files processed by the < > construct are to be edited in place.

-IDIR

with -P, tells the C preprocessor where to look for include files. The directory is prepended to @INC.

-l [OCTNUM]

enables automatic line-end processing, e.g., -l013.

-n

assumes an input loop around your script. Lines are not printed.

-p

assumes an input loop around your script. Lines are printed.

 

-P

runs the C preprocessor on the script before compilation by Perl.

-s

interprets -xxx on the command line as a switch and sets the corresponding variable $xxx in the script.

-S

uses the PATH environment variable to search for the script.

-T

forces taint checking.

-u

dumps core after compiling the script. To be used with the undump(1) program (where available).

-U

allows perl to perform unsafe operations.

-v

prints the version and patchlevel of your Perl executable.

-w

prints warnings about possible spelling errors and other error-prone constructs in the script.

-x [DIR]

extracts Perl program from input stream. If DIR is specified, switches to this directory before running the program.

-0VAL

(that's the number zero.) Designates an initial value for the record separator $/. See also -l

Literals

Numeric:

123

1_234

123.4

5E-10

0xff (hex)

0377 (octal)

String:

'abc'

literal string, no variable interpolation or escape characters, except \' and \\. Also: q/abc/. Almost any pair of delimiters can be used instead of /.../.

 

"abc"

Variables are interpolated and escape sequences are processed. Also: qq/abc/.
Escape sequences: \t (Tab), \n (Newline), \r (Return), \f (Formfeed), \b (Backspace), \a (Alarm), \e (Escape), \033 (octal), \x1b (hex), \c[ (control)
\l and \u lowercase/uppercase the following character. \L and \U lowercase/uppercase until a \E is encountered. \Q quote regular expression characters until a \E is encountered.

`COMMAND`

evaluates to the output of the COMMAND. Also: qx/COMMAND/.

 

Array:

(1, 2, 3). () is an empty array.
(1..4) is the same as (1,2,3,4),
likewise ('a'..'z').
qw/foo bar .../ is the same as ('foo','bar',...).

Array reference:

[1,2,3]

Hash (associative array):

(KEY1, VAL1, KEY2, VAL2,...)
Also (KEY1=> VAL1, KEY2=> VAL2,...)

Hash reference:

{KEY1, VAL1, KEY2, VAL2,...}

Code reference:

sub {STATEMENTS}

Filehandles:

<STDIN>, <STDOUT>, <STDERR>, <ARGV>, <DATA>.
User-specified: HANDLE, $VAR.

Globs:

<PATTERN> evaluates to all filenames according to the pattern. Use <${VAR}> or glob $VAR to glob from a variable.

Here-Is:

<<IDENTIFIER
Shell-style "here document."

Special tokens:

__FILE__: filename; __LINE__: line number; __END__: end of program; remaining lines can be read using the filehandle DATA.