I am working on a little module to scan a whole tree of sourcefiles for use with Vim. One of the methods is:

sub parseDir {
    my $self    = shift;
    my $path    = shift;  # the path to the directroy we are
                          # currently scanning.
    my $out     = shift;  # the file we write the results to
    my $target  = shift;  # the thing we are searching for

    my $dir = IO::Dir->new($path) or die "can't open $path : $!";
    my @files = $dir->read();
    $dir->close();
    # Scan all interesting files
    grep(   ( -f "$path/$_" ) and 
            ( $_ =~ m/\.(java|xml|cpp|c|h|inc|pas)$/i ) and
            ( $self->Scan_File( "$path/$_", $out, $target ) )  , @file
+s );
    # Also scan any subdirectories.
    grep( ( ( -d "$path/$_" ) and 
            ( $_ !~ /^\.+$/ ) and # but avoid . and ..
            ( $self->parseDir( "$path/$_", $out, $target ) ) ), @files
+ );
}
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The odd thing is that the second grep works fine while the first grep results in a: 'Not enough arguments for grep at scan.pl line 63, near "@files )"'. The only difference between the two is that the first has a '(' ')' pair less. I am quite puzzled why this makes a difference, since both

 
  ( expression ) and ( expression ) and ( expression)
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and

 
  ( ( expression ) and ( expression ) and ( expression) )
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seem to me to be syntactically correct expression.

Can anybody shed some light on this?