Check nesting IF-ELSE-ENDIF in Config Files

Sometimes tracing down the build problems caused by wrong configuration files (platform.bib/.reg/...) is hard due to lot's of IF-ELSE-ENDIF statements (see an older post: "Strange build error message").

Last time I was bugged by a totally messed up configuration file and therefore I wrote (better say 'hacked') a little perl script that just lists the nesting level of each IF, ELSE, ENDIF statement.

Here's the full code - enjoy. There is room for improvements and hints/comments are welcome (I'm definitely not a perl guru :-)

@goto ;#DOS

##
# Visualize nesting level of IF/ELSE/ENDIF pairs
# Dr. Jürgen Welzenbach, 2009
#

# - Constants -------------------------
my $tag_Begin = "IF";
my $tag_Mid   = "ELSE";
my $tag_End   = "ENDIF";

## - Preamble -------------------------------------------------------
use strict;
use Cwd;
use File::Basename;

my $nestingWidth = 5;


## - Main -----------------------------------------------------------
&filter_files( @ARGV );

## - Functions ------------------------------------------------------
sub filter_file
{
   my $fname = shift;
   my($filename, $directories, $suffix) = fileparse($fname, qr/\.[^.]*/);
   my $nestCount = 0;
   my $lineNo = 1;

   print "Checking $fname\n";
   my $fname_ok    = open( FILE,    "<", $fname );     if ( $fname_ok )     {         my $line;          print("Line Level  Text:\n");         while ( $line =  )
       {
           my $printIt = 0;
           $line = " " . $line;
           ## Ok, here's room for improovement; but I'm no perl specialist and for
           ## a quick hack it's ok - for the moment :-)
           if ( $line =~ /\W$tag_Begin/ )
           {
               $line =~ s/^\s+//;
                my $sp = sprintf("%4d [%2d]: %*s%s", $lineNo, $nestCount, ($nestCount*$nestingWidth), " ", $line);
                print $sp;
                $nestCount = $nestCount + 1;
           }
           elsif ( $line =~ /\W$tag_Mid/ )
           {
               $line =~ s/^\s+//;
                my $sp = sprintf("%4d [%2d]: %*s%s", $lineNo, $nestCount, (($nestCount-1)*$nestingWidth), " ", $line);
                print $sp;
           }
           elsif ( $line =~ /\W$tag_End/ )
           {
               $line =~ s/^\s+//;
                $nestCount = $nestCount - 1;
                my $sp = sprintf("%4d [%2d]: %*s%s", $lineNo, $nestCount, ($nestCount*$nestingWidth), " ", $line);
                print $sp;
           }

           $lineNo = $lineNo + 1;
       }
       close( FILE );
       warn $@ if $@;

   }
   else
   {
       if( !$fname_ok )
       {
           print "Error opening '$fname '\n";
       }
       else
       {
           close( FILE );
       }
   }
}

sub filter_files
{
   my @args = @_;

   while ( $#args >= 0 )
   {
       filter_file( $args[ 0 ] );
       shift @args;
   }
}


__END__

:;#DOS

@perl -S %0 %*