Since nobody's mentioned it yet, you should

use warnings;
use strict;
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[grin]

You should also validate the user's input. Never trust a user to do the right thing - even if you're the user. We all have our senior moments.

{
    # For the sake of the example, this assumes that you
    # want to limit the possible input to this range
    print "Please enter a number [1-9999]: ";
    chomp($in = <STDIN>);
    redo unless $in =~ /^\d+$/ && $in > 0 && $in <= 9999;
}

print join(",", 1 .. $in), "\n";
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Last but not least, if you decide to not use the '..' range operator, you can do this in any number of silly ways:

print $in--; do { print ", $a" } while --$a;
for ($i=1;$i <= $in; $i++){ print $i-1?",$i":$i; }
while($in){push @a, $in--;} print join ",", reverse @a;
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...but you're better off sticking with the tried and true.