use strict;
use warnings;

my $ip;

open CMD, '-|' or exec qw(/sbin/ifconfig ppp0) or die "exec failed: $!";
foreach(<CMD>)
{
        $ip = $1 if m/^\s*inet addr:([0-9.]+)/;
}
close CMD;

print $ip ? "Deine IP: $ip\n" : "IP nich gefunden :-(\n";