use strict;
use warnings;

for my $string (
    '/Unixish path/with/spaces in places/and a file name with spaces',
    'file name only - with spaces',
    '/nice/no/spaces/path/and/filename'
    )
{
    if ($string =~ m!(.*/)?(.*)!) {
        print "Path = '$1', Filename = '$2'\n";
    } elsif ($string =~ /(\S+)/) {
        print "No path, Filename = '$2'\n";
    }
}

##</code><code>##

Path = '/Unixish path/with/spaces in places/', Filename = 'and a file name with spaces'
Path = '', Filename = 'file name only - with spaces'
Path = '/nice/no/spaces/path/and/', Filename = 'filename'