A perl script which can replace tab to 4 spaces in source files under an argument(dir).

replaceTabToSpace.pl

use strict;
use warnings;
use File::Basename 'fileparse';

my $dir = $ARGV[0];
if(! -d $dir){
    die "Invalid argument.";
}
$dir =~ s|\\|/|g; # Just in case.

my @fileList;
getFileList($dir, \@fileList);

foreach my $file (@fileList){
    if(-f $file){
        my($basename, $dirname) = fileparse($file);
        my $outFile = "$dirname/$basename.replaced";
        
        open(IN, $file);
        open(OUT, ">$outFile");
        
        foreach my $line (<IN>){
            $line =~ s/\t/    /g;
            print(OUT $line);
        }
        close(IN);
        close(OUT);
        rename($outFile, $file);
    }
}


sub getFileList{
    my $dir = shift;
    my $ref_fileList = shift; # for output.
    
    opendir(DIR, $dir);
    my @fileList = readdir(DIR);
    closedir(DIR);
    
    foreach my $file (sort @fileList){
        if($file =~ /^\.{1,2}$/){
            next;
        }
        
        if( -d "$dir/$file"){
            getFileList("$dir/$file", $ref_fileList);
        }
        else{
            push(@$ref_fileList, "$dir/$file");
        }
    }
}