Difference between \z and \Z and \a and \A in Perl

Question

Can you please tell me the difference between \\z and \\Z as well as \\a and \\A in Perl with a simple example ?

Answer 1

The following indicates the positions at which the relevant regex patterns will match (␊ indicates a line feed):

\A                       \A is not affected by /m
^                        ^ without /m             ≡ \A
^/m  ^/m  ^/m            ^ with /m                ≡ \A|(?<=\n)
|    |    |
|    |    |
v    v    v
abc␊def␊ghi␊
   ^    ^    ^^
   |    |    ||___
   |    |    |    |
   $/m  $/m  $/m  $/m    $ with /m                ≡ (?=\n)|\z
             $    $      $ without /m             ≡ (?=\n\z)|\z
             \Z   \Z     \Z is not affected by /m ≡ (?=\n\z)|\z
                  \z     \z is not affected by /m

\a is equivalent to \x07, meaning it matches character 0x07 (BEL/BELL in ASCII and UNICODE).

This is documented in perlre.