Linux Ask!

Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.

Sep 262011
 

Enable Perl strict mode to restrict unsafe constructs

Answer:

In Perl, you can enforce using the strict mode to reduce the chance of nasty error, e.g.

$foo = 'bar';
print $foo;

If you run the above problem, it is completely valid.

# perl test.pl
bar

However, if you use the strict pragma

use strict;

$foo = 'bar';
print $foo;

And run the program again..

# perl test.pl
Global symbol "$foo" requires explicit package name at test.pl line 3.
Global symbol "$foo" requires explicit package name at test.pl line 4.
Execution of test.pl aborted due to compilation errors.

Since the $foo is not declared before the first use, so the compilation stopped. In modern Perl developements, it is recommended to alwasys use the strict pragma in order to write a better and maintainable program.

To fix the problem, you need to use the my keyword, e.g.

use strict;

my $foo = 'bar';
print $foo;

And run the program again. (Thanks Jeroen for the suggestion)

Jan 022011
 

Multi-line string in Perl

Answer:

To assign a multi-line string to a variable in Perl, is easy with the following trick:

my $html = <<END;
<p>
    This is HTML content.
</p>

END

print $html;
Dec 212010
 

How can I find out my current package in Perl?

Answer:

To find the current package in your Perl script, you can try something like the following:

package Foo;

my $current_package = __PACKAGE__;
print "I am in package $current_package\n";

1;

When executed:

# perl foo.pl

I am in package Foo