Karger78 has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I have a quick regex question. How would i match anything up until the 3rd under score and store it in an var? So for a file name, everything up until the 3rd _. Thanks in advance.

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Re: Quick regex
by BrowserUk (Patriarch) on Nov 24, 2009 at 17:14 UTC

    Like this? 

    $s = 'fred_bill_john_jack_joe_mary_eugene';;

$s =~ /(^[^_]+_[^_]+_[^_]+_)/ and print "'$1'";;

'fred_bill_john_'

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    Or this? 

    $s =~ /(^(?:[^_]+_){3})/ and print "'$1'";;

'fred_bill_john_'

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    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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      that looks good, but how do i kill the trailing _ So your example would look like this 'fred_bill_john'
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        You want to match 

        name, dash, name, dash, name

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        or 

        ( name, dash ) x 2, name

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        so 

        my ($substr) = $s =~ /^((?:[^_]*_){2}[^_]*)/
    or die("No match\n");

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        Everything in ( ) goes into $1, so move the last _ outside of )
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Re: Quick regex
by Anonymous Monk on Nov 24, 2009 at 17:10 UTC
    This is probably faq 
    print $1 if "ab _ cd _ ef _ gh " =~ /(.*?(_).*?\2.*?)\2/;
__END__
ab _ cd _ ef

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