my $data = XMLin("C:\\core\\jobs_1.xml");
#works perfectly
my $filename = $config->{'DRIVE'}.$config->{'JOBS_XML_FILE'}
print $filename."\n"; 
my $data = XMLin($filename);

__OUTPUT__
C:\\core\\jobs_1.xml
panic: pp_match start/end pointers at C:/Perl/lib/File/Basename.pm line 186.