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Re: Meaning of /o in Regexes

by cjf-II (Monk)
on Dec 06, 2002 at 12:30 UTC ( #218049=note: print w/replies, xml ) Need Help??

in reply to meaning of /o in regexes

The /o modifier is used when you only want the pattern compiled once. So in the second pattern, $x will not be incremented and as such, only matches once.

Update: Okay, I promise to read the questions in full before replying from now on (and this time I mean it! ;-). So to answer your actual question...

The difference between qr// and the /o modifier as I understand it is that with /o you can never change the pattern, whereas with qr// you can compile the pattern to be used as part of a larger regex. As the good book shows:

@regexes = (); for $pattern (@patterns) { push @regexes, qr/$pattern/; } for $item (@data) { for $re (@regexes) { if ($item =~ /$re/) { print "Matches!\n"; } } }

I Hope that's slightly more helpful :).

Replies are listed 'Best First'.
Re: Re: Meaning of /o in Regexes
by mce (Curate) on Dec 06, 2002 at 12:45 UTC
    Thanks, But this part I understood, it is the comparison with qr that I am puzzeled about.
    Dr. Mark Ceulemans
    Senior Consultant
    IT Masters, Belgium

      Thanks, But this part I understood, it is the comparison with qr that I am puzzeled about.

      /o and qr// provide different services to the programmer:

      /o says 'Take this pattern and create a compiled regex that will not change for the life of the program'

      qr// says 'Take this pattern and return a special object that I can assign to a variable, interpolate into another pattern, pass to a subroutine, etc, etc, and as a side-effect creates a compiled form that I can use in pattern matches directly.'

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