This one will work on Perl 5.8 (and probably much earlier)

gistfile1.pl

#!/usr/bin/env perl

use strict ;
use warnings;
use locale ;

my @table=(1,2,3,8,5,8,0,4) ;
my @places ;

# Max value
my $max = (sort @table)[-1];

# Position
for my $index (0..$#table) {
    push @places, $index if $table[$index] == $max;
}

print "Max value is \"$max\", at position(s) " . join(", ", @places) . "\n" ;