regex - Perl 正则表达式单词匹配

Question

如何使用 perl regexp 匹配以下字符串？

$line="virtual void function";
$line="virtual function";
$line="void function";
$line="function";
$line="pure virtual function";
$line="extern function";
$line="extern void function";

即匹配 0 或 n 个由至少一个空格分隔的函数限定符，后跟字符串“function”。

它不应该匹配

$line="// function";
$line="asdfgh";     
$line="endfunction";     

有没有类似的东西

$line=~/^([evp\s]*) function/ ;

哪个可以用于单词而不是字符？

Answer 1

(?:PAT1|PAT2)是模式和[ab]字符。

/^(?:(?:extern|pure|virtual|void)\s+)*function/

Answer 2

我想出了一个看起来很像 ikegami 的解决方案：

#!/usr/bin/env perl
use strict;
use warnings;

my @lines = (
    "virtual void function",
    "virtual function",
    "void function",
    "function",
    "pure virtual function",
    "extern function",
    "extern void function",
    "// function",
    "asdfgh",
    "endfunction",
);

foreach my $line (@lines) {
    if ($line =~ m{^((virtual|void|pure|extern)\s+)*function}) {
        print "$line is a " . ($1||"'plain function'") . "\n";
    }
    else {
        print "ignored: $line\n";
    }
}

产生：

$ perl 17662838-perl-regex-word-matching.pl
virtual void function is a void
virtual function is a virtual
void function is a void
function is a 'plain function'
pure virtual function is a virtual
extern function is a extern
extern void function is a void
ignored: // function
ignored: asdfgh
ignored: endfunction