Actually, the two code snippets work exactly the same. Witness:

$ cat x.pl
foreach(glob('*.*')) { unlink if -f and !-s _; }
foreach(glob('*.*')) { unlink if (-f $_) && !-s _; }

$ perl -MO=Deparse x.pl
use File::Glob ();
foreach $_ (glob('*.*')) {
    unlink $_ if -f $_ and not -s _;
}
foreach $_ (glob('*.*')) {
    unlink $_ if -f $_ and not -s _;
}
x.pl syntax OK
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