Printing Environment Variables Using Perl One Liner

Solution 1

C:\Documents and Settings\sivkumar>perl

use Data::Dumper;
print Dumper \%ENV;


Solution 2 - Perl One Liner

perl -MData::Dumper -e "print Dumper \%ENV"

Tilde-Tilde Operator

A bit obscure is the tilde-tilde "operator" which forces scalar context.

print ~~ localtime;

is the same as

print scalar localtime;

and different from

print localtime;

Spaceship Operator.

Easy with the Spaceship Operator.

$a = 2 <=> 5;  # $a is set to -1
$a = 5 <=> 2;  # $a is set to 1
$a = 2 <=> 2;  # $a is set to 0

Non-Obvious features in perl.

For example, did you know that there can be a space after a sigil?

 $ perl -wle 'my $x = 3; print $ x'
3

Or that there you can give subs numeric names if you use symbolic references?

$ perl -lwe '*4 = sub { print "yes" }; 4->()' 
yes

There's also the "bool" quasi operator, that return 1 for true expressions and the empty string for false:

$ perl -wle 'print !!4'
1
$ perl -wle 'print !!"0 but true"'
1
$ perl -wle 'print !!0'
(empty line)

Other interesting stuff: with use overload you can overload string literals and numbers (and for example make them BigInts or whatever).

Many of these thins are actually documented somewhere, or follow logically from the documented features, but nonetheless some are not very well known.

Update: Another nice one. Below the q{...} quoting constructs were mentioned, but did you know that you can use letters as delimiters?

$ perl -Mstrict  -wle 'print q bJet another perl hacker.b'
Jet another perl hacker.

Likewise you can write regexes

m xabcx
# same as m/abc/