Indeed. Quoting and a bit paraphrasing "Mastering Regular Expressions 2nd Edition": 
A match mode can change the meaning of "$" to match before any embedde
+d newline (or Unicode line terminator as well). When supported, "\Z" 
+usually matches what the "unmoded" "$" matches, which often means to 
+match at the end of the string, or before a string-ending newline. To
+ complement these, "\z" matches only at the end of the string, period
+, without regard to any newline.
..
//s stands for Single Line Mode which makes the dot match any characte
+r.
..
//m stands for Multi Line Mode which changes how ^& $ are considered b
+y the regex engine. ^ is then begin of 1 line out of the many lines i
+n the string and not begin of string and $ is end of 1 line out of th
+e many lines in the string and not end of string.
..
Caret "^" matches at the beginning of the text being searched, and, if
+ in an enhanced line-anchor match mode after any newline.
..
\A always matches only at the start of the text being searched, regard
+less of single or multi line match mode.
..
"\Z" matches what the "unmoded" "$" matches, which means to match at t
+he end of the string, or before a string-ending newline. To complemen
+t these, "\z" matches only at the end of the string, period, without 
+regard to any newline.

[download]
With thanks to Jeffrey Friedl's Regex Holy Book! ;-)

In reply to Re^3: Strange regex to test for newlines: /.*\z/ by ddn123456
in thread Strange regex to test for newlines: /.*\z/ by betterworld

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