my $filename = '/opt/netdb/netmacvendor/oui.txt';
open my $fh, '<', $filename
    or die "Couldn't read $filename: $!";

##</code><code>##

file:///opt/netdb/netmacvendor/oui.txt

##</code><code>##

file:/opt/netdb/netmacvendor/oui.txt

##</code><code>##

use URI::file;
print URI::file->new('/opt/netdb/netmacvendor/oui.txt');