Dear Monks,

I have questions regarding the "while" effect on regular expression matching process. Below is the code:

use v5.14;
while(<>) {
while( m/
        \b
        (\w\S+)
        (
            \s+
            \1
        ) +
        \b
        /xi  #if add modifier "g", it works fine.
)
{
say "dup word '$1' at paragraph $.";
}
}

[download]

My questions are:

1. This code will produce the first matched duplicate word infinitely. It seems that the second "while" evaluate the condition of regex matching unlimited times. Why doese this happen? Does the matching only happen once?

2. But if I add "g" modifier to the regex matching, it will accurately produce all the matched strings once and stop. Why does this happen?

3. What is the effect of second "while"? when a "while" used in a regex pattern matching statement, what is the behavior of "while",or how many times will "while" evaluate regex conditions, especially with or without modifier "g"?

Thank you.

In reply to "While" effect on regex? by lightoverhead

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