Check to see if your code is what you thought it was, using B::Deparse (Tip #6 from the Basic debugging checklist) :

use File::Glob ();
foreach $file (glob('*.*')) {
    if ($file =~ /\.c/) {
        $filename = $file;
        print /$filename\n/;
    }
}
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As Anon points out, you're really using m///