Constructs
C-style loops are usually unnecessary
- You can do C-style for loops, but you often don't need them
- Don't use them where a foreach will do
for (my $i = 0; $i <= $#foo; $i++) { # BAD foreach (@foo) { # BETTER - Don't use them where a while will do
for (my $i = <STDIN>; $i; $i = <STDIN>) { # BAD while (my $i = <STDIN>) { # BETTER - Think about what you're coding and do what makes sense
Anonymous hashes & arrays
- Create an anonymous array reference, and assign it:
my $array = [ 'one', 'two', 'three' ]; - This is "anonymous" because we didn't have to create an array
- Hashes have a similar constructor
my $hash = { one => 1, two => 2, three => 3 }; - Treat as you'd otherwise treat a reference
q[qrwx]?//, m//, s/// and y///
- Perl lets you specify your own delimiters for:
- Single quotes: 'text' => q/text/
- Double quotes: "text" => qq/text/
- Regular expressions: qr/text/
There is no other way to specify a regular expression match like this in Perl outside of a match or substitution operation.
- Words: ("text", "text") => qw(text text);
- Backticks: `text` => qx/text/
- Regex match (
m//), Regex substitute (s///), and translate (tr///,y///) work the same way
- You can use any character except whitespace.
- But use something balanced like parens or braces
qq// qq#A decent <html> delimiter </html> # qq( man perl(1) for details ) # valid!
global, local, my, our
- Declare global variables with
use vars. - Declare lexical variables with
my localis not what you think, usemyinstead unless you know why you're using local- Use
ouronly when your package needs a global variable
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