If I understand you correctly, you are wanting to do the equivalent of: 

grep -v IPADDR "$dir/$sys/$ifdir/$if0" > "$dir/$sys/$ifdir/${if0}.new"
echo "IPADDR=1.1.1.1" >> "$dir/$sys/$ifdir/${if0}.new"

[download]

at the command line. If this is the case, do you really need perl for this or is this part of a larger script/problem?

--gsiems

Update: Looking closer, I see that I missed the BOOTPROTO line. Is this closer to what you are looking for (not tested): 

print "Please enter the ip address for this machine.  This will be eth
+0:\n";
my $ip = <>;
chomp $ip;

my $if0 = "ifcfg-eth0";
my $if1 = "ifcfg-eth1";
my $ifdir = 'network-scripts';
my $ifsub1 = "IPADDR=";
my $ifsub2 = "BOOTPROTO=";
my $ifsub3 = "none";

my $IP;
my $NEW;

open ($IP, "<", "$dir/$sys/$ifdir/$if0");
open ($NEW, ">", "$dir/$sys/$ifdir/$if0.new");

my @ary = ( grep { $_ !~ m/IPADDR/ } (<$IP>));
s/($ifsub2).+$/$1$ifsub3/ for @ary;
print $NEW @ary;
print $NEW "IPADDR=$ip\n";

close $IP;
close $NEW;

[download]

In reply to Re: How to write a new line in a while loop? by gsiems
in thread How to write a new line in a while loop? by xjlittle

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.