Annoying error although module is installed

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,
I am trying to use some of Perl's built-in statistical functions, namely to calculate standard deviation and mean of a list.
I install the two modules:

install Statistics::Basic::Median
Statistics::Basic::Median is up to date (undef).

install Statistics::Basic::StdDev
Statistics::Basic::StdDev is up to date (undef).
[download]

however this code:

use Statistics::Basic::StdDev;
my $stddev = stddev(1,2,3);
print $stddev."\n";
[download]

returns:

Undefined subroutine &main::stddev called at test.pl line 2.
[download]

What am I doing wrong?

Comment on Annoying error although module is installed Select or Download Code

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Re: Annoying error although module is installed by tangent (Parson) on Feb 28, 2016 at 22:49 UTC
stddev() is not a built-in function, it is a function provided by the module. From looking at the docs that module does not export any functions by default so you will need to import them before using them: `# you can remove this line use Statistics::Basic::StdDev; # add this line use Statistics::Basic qw(:all);` [download] You can then use all the functions in your script.	[reply] [d/l]
Re: Annoying error although module is installed by GrandFather (Saint) on Feb 29, 2016 at 00:43 UTC
In addition to the import techniques described above you may instead specify the module in the call: `use Statistics::Basic::StdDev; my $stddev = Statistics::Basic::StdDev::stddev(1,2,3); print $stddev."\n";` [download] which helps maintenance in a large script by making it clear where `stddev` comes from. Premature optimization is the root of all job security	[reply] [d/l] [select]
Re: Annoying error although module is installed by 1nickt (Canon) on Feb 28, 2016 at 22:48 UTC
You're not importing the method before you use it. `use Statistics::Basic::StdDev 'stddev';` [download] Untested... could also be: `use Statistics::Basic 'stddev';` [download] Hope this helps! edit: tangent's answer is more complete. The way forward always starts with a minimal test.	[reply] [d/l] [select]
Re^2: Annoying error although module is installed by Anonymous Monk on Feb 29, 2016 at 00:21 UTC
Thank you very much!	[reply]