while (<>) {
    # some code
}

Is short for:

while ( @ARGV ) {
    $ARGV = shift @ARGV;
    open ARGV;
    while ( defined( $_ = <ARGV> ) ) {
        # some code
    }
}

So you are reading from the files listed on the command line and using their contents as the file names to stat.    Perhaps you meant to do something like this instead:

for ( @ARGV ) {
    my @answer = filetest( $_ );
    print @answer;
}
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