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How can I comment out a large block of Perl code?
Answer:
Perl does not support multi-line comments like C++ or Java. If you want to comment out a large block of Perl code, there is still a trick.
package Foo;
=pod
This is a multi-line comments
more...
more...
=cut
print "Hello";How to find a Perl Module's Path
Answer:
For example, we want to know where the module JSON and related modules exist in the local file system, we can try:
# perl -MJSON -e'print $_ . " => " . $INC{$_} . "\n" for keys %INC'
attributes.pm => /usr/share/perl/5.10/attributes.pm
XSLoader.pm => /usr/local/lib/perl/5.10.0/XSLoader.pm
warnings/register.pm => /usr/share/perl/5.10/warnings/register.pm
Carp.pm => /usr/share/perl/5.10/Carp.pm
Exporter/Heavy.pm => /usr/share/perl/5.10/Exporter/Heavy.pm
common/sense.pm => /usr/local/share/perl/5.10.0/common/sense.pm
vars.pm => /usr/share/perl/5.10/vars.pm
Exporter.pm => /usr/share/perl/5.10/Exporter.pm
strict.pm => /usr/share/perl/5.10/strict.pm
constant.pm => /usr/local/share/perl/5.10.0/constant.pm
warnings.pm => /usr/share/perl/5.10/warnings.pm
JSON/XS.pm => /usr/local/lib/perl/5.10.0/JSON/XS.pm
overload.pm => /usr/share/perl/5.10/overload.pm
base.pm => /usr/share/perl/5.10/base.pm
JSON.pm => /usr/local/share/perl/5.10.0/JSON.pm
How to get the full list of Ubuntu's managed Perl modules?
Answer:
The full list of Ubuntu's managed Perl modules is here (for lucid): http://packages.ubuntu.com/lucid/perl/
You can use apt-get into install those modules, instead of CPAN. The advantage is you can remove them easier with the apt-get command, while for CPAN, you need to do it manually.
Write to the middle of a file in Perl
Answer:
To write to the middle of a text file, can be easily performed by Perl.
Assume the file has 10 lines, you want to replace the 5th line:
#!/usr/bin/perl
use strict;
use Tie::File;
my $file = 'foo.txt';
tie @array, 'Tie::File', $file or die "Cannot open $file \n";
@array[4] = "Replaced!\n";
That's easy?
What is the difference between || and or in Perl?
Answer:
In Perl, sometimes you can use both `||` and `or` to to do the same thing. But the main different is:
Example:
open FILE, $file or die("Cannot open $file"); # Work
open FILE, $file || die("Cannot open $file"); # Does not work , because it it same as the next statement
open FILE, ($file || die("Cannot open $file")); # Obviously not work
