regex - perl中的qr//是什么意思

Question

我对 Perl 完全陌生，并试图设计一个我遇到的词法分析器:

my @token_def =
 (
        [Whitespace => qr{\s+},     1],
        [Comment    => qr{#.*\n?$}m,   1],
  );

即使浏览了多个网站我也不明白其含义。

Answer 1

qr// 是适用于模式匹配和相关事件的类似引号的运算符之一。

来自perldoc :

This operator quotes (and possibly compiles) its STRING as a regular expression. STRING is interpolated the same way as PATTERN in m/PATTERN/. If ' is used as the delimiter, no interpolation is done.

来自modern_perl :

The qr// operator creates first-class regexes. Interpolate them into the match operator to use them:

my $hat = qr/hat/;
say 'Found a hat!' if $name =~ /$hat/;

...或将多个正则表达式对象组合成复杂的模式:

my $hat   = qr/hat/;
my $field = qr/field/;

say 'Found a hat in a field!'
if $name =~ /$hat$field/;

like( $name, qr/$hat$field/,
            'Found a hat in a field!' );