Update: The OP has made major changes since I posted this (only an un-indented sub was provided)...

Is it "not working" because you're not calling the function, perhaps? It seems to work for me for one set of inputs:

use warnings;
#use strict;

print min(qw(5 3 9 8)), "\n";

sub min {
    my (@num);
    @num = @_;
    $min = $num[0];
    foreach $i (@num) {
        if ( $i < $min ) {
            $min = $i;
        }
    }
    return $min;
}

__END__

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• Before you post, run your code through perltidy
• use strict and warnings (I'm repeating myself)
• Describe what you mean by "not working"
• If you want something that is mature and has been thoroughly tested, use List::Util::min