my $tablength = 4;

my $string = "\tSample\ttext.";

my $expanded_length = render_length($string, $tablength);

sub render_length {
    my ($string, $tabl) = @_;
    my $length = length($string);
    my $tabcount = $string =~ tr/\t//;
    $length += ($tabl - 1) * $tabcount;
    return $length;
}