My Windows background has found me out...

$, = ', ';
my @files;
print ((-e $data)? $data : ((@files = glob $data) && ($data ne $files[
+0]))? @files : ()) if $data;
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Prints $data if $data is a file. Prints the globbed $data only if the glob did some work. The whole statement is protected just in case $data is empty.