First, your $errorstate variable is named the opposite of what it should be. You set it to 1 when the input is formatted properly! Then, the bottom half of your code can be idiomized using some built-in variables in Perl. And are you sure you want to REMOVE the '#' from lines starting with '#port'? You also do some unnecessary work of checking to see if a regex matches before doing a substitution using that regex.

It turns out you can get rid of $errorstate altogether, and just loop until $sshport has a value. 

#!/usr/bin/perl

use strict;
use warnings;

my $sshport = 0;

until ($sshport) {
  print "Please enter SSH port number> ";
  chomp($sshport = <STDIN>);
  $sshport = 0 unless $sshport =~ /^[1-9]\d{1,9}$/;
}

{
  local $^I = ".old";             # the "in-place edit backup extensio
+n" variable
  local @ARGV = ("sshd_config");  # the files to edit in-place

  while (<>) {
    s/^(#?)port .*/$1Port $sshport/i;
    # this KEEPS the '#' character,
    # which I think is the correct behavior
  }
}

[download]
See perlvar for information about $^I.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re: Defactor this code by japhy
in thread Defactor this code by xerophyte

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