[nagiosplug] Use own variable instead of ENV

[Nagios Plugin Development]

 Module: nagiosplug
 Branch: hw/update-pm
 Commit: af85216c79e267b2f586064a1f7e3e01a4277d75
 Author: Ton Voon <ton.voon at opsera.com>
   Date: Fri Aug 23 17:13:09 2013 +0100
    URL: http://nagiosplug.git.sf.net/git/gitweb.cgi?p=nagiosplug/nagiosplug;a=commit;h=af85216

Use own variable instead of ENV

---

 tools/build_perl_modules |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tools/build_perl_modules b/tools/build_perl_modules
index 57d6e61..9b0c3c2 100755
--- a/tools/build_perl_modules
+++ b/tools/build_perl_modules
@@ -256,7 +256,7 @@ foreach my $tarball (@tarballs) {
         # Need to set this so that XML::SAX will install ParserDetails.ini by finding the right XML::SAX copy
         # Also makes sense to do this anyway, as I guess CPAN must be doing this for it to usually work
         my $saved_PERL5LIB = $ENV{PERL5LIB};
-        $ENV{PERL5LIB} = "$ENV{DESTDIR}/$prefix/lib:$saved_PERL5LIB";
+        $ENV{PERL5LIB} = "$destdir/$prefix/lib:$saved_PERL5LIB";
         if ( -f "Build" ) {
             system("./Build install") == 0
                 or die "Can't run make install: $!\n";