Your code has an error. It reports the wrong number of leading tabs if there are some characters in the line that you didn't cater for:

sub countLeadingTabSpaces {
    my($data) = @_;
    my @string=split(/\t/,$data);
        my $numberofLeadingTabs=0;
        my $size = @string;
        my $TabSpace = "";
        my $loopBreak = 0;
        for (my $count = 0; $count < $size; $count++)
        {
            if($loopBreak==0)
            {
                if($string[$count] =~/([A-Za-z0-9@])/)
                {
                    $loopBreak = 1;
                }else{
                    ++$numberofLeadingTabs;
                }
            }
        }        
        print "=>NumberofLeadingTabs: ".$numberofLeadingTabs;
        return $numberofLeadingTabs;
}

countLeadingTabSpaces("\t\t!\tfoo"); # prints "3" but only has two lea
+ding tabs!
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It's better to avoid split and then checking whether a line contains a certain set of characters, and instead just count the number of tab characters at the start:

my $numberofLeadingTabs = 0;
if ($data =~ /^(\t+)/) {
    my $tabs = $1;
    $numberofLeadingTabs = length $tabs;
};
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