Sorry, I am very frustrated right now. I have spent the last six hours trying to come up with a simple perl program to list all permutations for the numbers from one to five (the use of cpan modules is not allowed for this exercise).

The well-known algorithm and code snippets in other languages can be found here:

http://stackoverflow.com/questions/9148543/program-to-print-permutations-of-given-elements

One python implementation is very brief and almost understandable (though my python knowledge is even poorer than my perl knowledge): 

def permute(in_str, prefix=""):
    if not len(in_str) :
        print(prefix)
    else:        
        for i in range(0, len(in_str)):

            permute(in_str[:i] + in_str[i + 1:], prefix + in_str[i])
permute('12345')

[download]
The biggest problem is (even after reading man perlsub for over an hour), I just don't understand the calling syntax. My attempt is looking something like this (which generates a huge number of syntax errors and won't run). 
#!/usr/bin/perl -w
use strict;

my @array = 1..5;

while (permute @array)

sub permute
    {
    my @temp;
    while ( $#temp < $#_)

        {
        my $i;
        for ($i = $#temp; $i < $#_; $i++)

            {
            swap @_[$i] @_[$#temp];
            permute;
            swap @_[$i] @_[$#temp];
            }
        }

    print $_;
    }

sub swap
    {
    my $k;
    my $l;
    my  $temp;
    $temp = $k;
    $k = $l;
    $l = $temp;
    }

[download]

Can someone guide me in the right direction. Clever techniques are not important. What is important is that I understand what is going on.

Thank you (very much) in advance.

In reply to generating permutations by Anonymous Monk

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