Programming Perl, 4th Edition

Endings: The \z, \Z, and $ Assertions

The \z metasymbol matches at the end of the string, no matter what’s inside. \Z matches right before the newline at the end of the string if there is a newline, or at the end if there isn’t. The $ metacharacter usually means the same as \Z. However, if the /m modifier was specified and the string has embedded newlines, then $ can also match anywhere inside the string right in front of a newline:

/bot\z/      # Matches "robot"
/bot\Z/      # Matches "robot" and "abbot\n"
/bot$/       # Matches "robot" and "abbot\n"
/bot$/m      # Matches "robot" and "abbot\n" and "robot\nrules"

/^robot$/    # Matches "robot" and "robot\n"
/^robot$/m   # Matches "robot" and "robot\n" and "this\nrobot\n"
/\Arobot\Z/  # Matches "robot" and "robot\n"
/\Arobot\z/  # Matches only "robot" — but why didn’t you use eq?

As with ^, the /m modifier lets $ match many times in the same string when used with /g. (These examples assume that you’ve read a multiline record into $_, perhaps by setting $/ to "" before reading.)

s/\s*$//gm;   # Trim trailing whitespace on each line in paragraph

while (/^([^:]+):\s*(.*)/gm ) {  # get mail header
    $headers{$1} = $2;
}

In Variable Interpolation, later in this chapter, we’ll discuss how you can interpolate variables into patterns: if $foo is “bc”, then /a$foo/ is equivalent to /abc/. Here, the $ does not match the end of the string. For a $ to match the end of the string, it must be at the end of the pattern or be immediately followed by a vertical bar or closing parenthesis. ...