perl

Perl tips

Install module in non-standard location

For whatever reason (maybe you don't have permission) you may want to install a Perl module outside the standard tree.

perl Makefile.PL PREFIX=/path/to/install

To build more modules, that depend on finding the modules you just installed (in a non-standard location), use this

PERL5LIB=/path/to/install perl Makefile.PL

Ignore uninitialized variable warnings

Sometimes you don't care about all those uninitialized variables, but don't want to give up warnings altogether.

no warnings 'uninitialized';

Determining if a module is in the path of @INC before using 'use' directive

wrap the 'use' in an 'eval' then wrap the 'eval' in a 'BEGIN' block

 BEGIN { unless (eval "use My::Mod") { warn "Couldn't load My::Mod: $@";}}

CPAN installs

Are you always seeing "junoscript-perl" in the list of modules to be installed, even though you did not request it? The solution is easy: stop using "install" when you run cpan from the command line.

      bad: 'cpan install My::Module'
     good: 'cpan My::Module'

use the Perl::Critic module

Try using Perl::Critic against all your code to find problems based on recommendations from Perl Best Practices book. This supplies a command line util perlcritic that you can run against your scripts or modules.

easy way to determine module versions

add the following to $HOME/.bashrc:

function pmver () { perl -M$1 -le "print $1->VERSION"; }

Don't forget to "source $HOME/.bashrc" for the change to take effect

Epoch time ==> human readable

#!/usr/bin/perl

my $epochtime = shift;
my $result = `date -d '1970-01-01 UTC +$epochtime seconds'`;
print $result;