You've already got answers to your questions, I just wanted to add: For some more info on strict see also Use strict and warnings. And, in this case, you can parameterize the width of a sprintf format without interpolating into the format string:

my $w = 5;
my $str = "abc";
my $line = sprintf "%*s", $w, $str;
print "<", $line, ">\n";
__END__
<  abc>
[download]

Update: Athanasius beat me to it ;-)