how does the regex like ".*" work in perl

Question

I am puzzled by regular expression like .*

#!usr/bin/perl
use strict;
use warnings;

my $text = "scott";
$text =~ s/.*/\//g;
print $text;

Output: //

So, I don't know why the result is // rather than /.

Answer 1

.* matches two times. First, it matches "scott". Then it matches the empty string after "scott".

Answer 2

The first time through, .* matches 5 characters starting at position zero (scott). This gets replaced with /.

/g means match as many times as possible, so it tries again, this time start at position five.

The second time through, .* matches 0 characters starting at position five (empty string). This gets replaced with /.

The third time through, .* goes to matches 0 characters starting at position five (""), but there's a check that makes sure it doesn't match the same starting position and length twice in a row. So it advances the position and tries to match at position six. Since that's outside the string it fails.