perl -dw ScriptName.pl Argument1 ... ...
Note that there is no limit to the number of arguments: Perl is polyadic; any number of arguments can be passed to any Perl subroutine, in general. This concept of "no arbitrary limits" is present in most other parts of the language as well. Perl can read a ten million byte string into a variable, if the machine has the memory for it.
== Perl 6 ==
Perl6 is currently under development, and is planned to separate parsing, compilation and runtime, making a virtual machine that is more attractive to developers looking to port other languages to the architecture.
[[Parrot virtual machine|Parrot]] is the Perl6 runtime, and can be programmed at a low level in [[Parrot assembly language]]. Parrot has existed in a limited form since December 2003. An increasing number of languages have been implemented to various degrees for the Parrot to be 'compiled' to Parrot assembly language opcodes. Besides a subset of the planned Perl6, these include [[BASIC programming language|BASIC]], [[Befunge]], [[Cola programming language|Cola]], [[Forth programming language|Forth]], [[Jako]], [[Ook!]], [[Plot programming language|Plot]], and even [[Python programming language|Python]], [[Ruby programming language|Ruby]], and [[Scheme]].
== Perl code samples ==
The canonical "[[hello world]]" program would be:
| Regular Expression | Description | Example
Note that all the if statements return a TRUE value |
|---|---|---|
| '''.''' | Matches an arbitrary character, but not a newline. |
$string1 = "Hello World\n";
if ($string1 =~ m/...../) {
print "$string1 has length >= 5\n";
}
|
| ( ) | Groups a series of pattern elements to a single element. When you match a pattern within parentheses, you can use any of $1, $2, ... $9 later to refer to the previously matched pattern. |
$string1 = "Hello World\n";
if ($string1 =~ m/(H..).(o..)/) {
print "We matched '$1' and '$2'\n";
}
Output:
We matched 'Hel' and 'o W';
|
| + | Matches the preceding pattern element one or more times. |
$string1 = "Hello World\n";
if ($string1 =~ m/l+/) {
print "There are one or more consecutive l's in $string1\n";
}
|
| ? | Matches zero or one times. |
$string1 = "Hello World\n";
if ($string1 =~ m/H.?e/) {
print "There is an 'H' and a 'e' separated by ";
print "0-1 characters (Ex: He Hoe)\n";
}
|
| ? | Matches the *, +, or {M,N}'d regexp that comes before as few times as possible. |
$string1 = "Hello World\n";
if ($string1 =~ m/(l+?o)/) {
print "The non-greedy match with one or more 'l' ";
print "followed by an 'o' is 'lo', not 'llo'.\n";
}
|
| * | Matches zero or more times. |
$string1 = "Hello World\n";
if ($string =~ m/el*o/) {
print "There is a 'e' followed by zero to many";
print "'l' followed by 'o' (eo, elo, ello, elllo)\n";
}
|
| {M,N} | Denotes the minimum M and the maximum N match count. |
$string1 = "Hello World\n";
if ($string1 =~ m/l{1,2}/) {
print "There exists a substring with at least 1";
print "and at most 2 l's in $string1\n";
}
|
| [...] | Denotes a set of possible matches. |
$string1 = "Hello World\n";
if ($string1 =~ m/[aeiou]+/) {
print "$string1 contains a one or more";
print "vowels\n";
}
|
| | | Matches one of the left or right operand. |
$string1 = "Hello World\n";
if ($string1 =~ m/(Hello|Hi)/) {
print "Hello or Hi is ";
print "contained in $string1";
}
|
| \b | Matches a word boundary. |
$string1 = "Hello World\n";
if ($string1 =~ m/\bllo\b/) {
print "There is a word that starts with";
print " 'llo'\n";
} else {
print "There are no words that start with";
print "'llo'\n";
}
|
| \w | Matches alphanumeric, including "_". |
$string1 = "Hello World\n";
if ($string1 =~ m/\w/) {
print "There is at least one alpha-";
print "numeric char in $string1 (A-Z, a-z, 0-9, _)\n";
}
|
| \W | Matches a non-alphanumeric character. |
$string1 = "Hello World\n";
if ($string1 =~ m/\W/) {
print "The space between Hello and ";
print "World is not alphanumeric\n";
}
|
| \s | Matches a whitespace character (space, tab, newline, formfeed) |
$string1 = "Hello World\n";
if ($string1 =~ m/\s.*\s/) {
print "There are TWO whitespace ";
print "characters separated by other characters in $string1";
}
|
| \S | Matches anything BUT a whitespace. |
$string1 = "Hello World\n";
if ($string1 =~ m/\S.*\S/) {
print "There are TWO non-whitespace ";
print "characters separated by other characters in $string1";
}
|
| \d | Matches a digit, same as [0-9]. |
$string1 = "99 bottles of beer on the wall.";
if ($string1 =~ m/(\d+)/) {
print "$1 is the first number in '$string1'\n";
}
Output:
99 is the first number in '99 bottles of beer on the wall.'
|
| \D | Matches a non-digit. |
$string1 = "Hello World\n";
if ($string1 =~ m/\D/) {
print "There is at least one character in $string1";
print "that is not a digit.\n";
}
|
| ^ | Matches the beginning of a line or string. |
$string1 = "Hello World\n";
if ($string1 =~ m/^He/) {
print "$string1 starts with the characters 'He'\n";
}
|
| $ | Matches the end of a line or string. |
$string1 = "Hello World\n";
if ($string1 =~ m/rld$/) {
print "$string1 is a line or string";
print "that ends with 'rld'\n";
}
|
| [^...] | Matches every character except the ones inside brackets. |
$string1 = "Hello World\n";
if ($string1 =~ m/[^abc]/) {
print "$string1 does not contain the characters a, b, and c\n";
}
|