G'day dicty,

\z is used in regular expressions as an anchor to match the end of a string (which could be multi-line). It differs from $ which matches the end of a line; and, it is subtly different from \Z (uppercase Z) which matches the end of the string but optionally before a newline if one exists.

The following code demonstrates each of these differences:

$ perl -Mstrict -Mwarnings -E '
    my $string = "abc\ndef\n";
    $string =~ /(.*?)$/ms;
    say q{[$]}, $1, q{[$]};
    $string =~ /(.*?)\z/ms;
    say q{[z]}, $1, q{[z]};
    $string =~ /(.*?)\Z/ms;
    say q{[Z]}, $1, q{[Z]};
'
[$]abc[$]
[z]abc
def
[z]
[Z]abc
def[Z]
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Under perlre - Regular Expressions, $ is described in the Metacharacters section and \z and \Z are described in the Assertions section.

I see hippo has answered your second question.