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

Hi Monks,

Why wouldnt this work 

($last_41) = $buffer =~ /(.*{41})$/;

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I need to get only the last 41 chars of the var $buffer into $last_41

Edited by Arunbear: Changed title from 'Why doesnt this work', as per Monastery guidelines

Replies are listed 'Best First'.
Re: Regex to match last n characters of a string
by BrowserUk (Patriarch) on May 13, 2005 at 06:18 UTC

    If you enable warnings you'll see 

    Nested quantifiers in regex; marked by <-- HERE in m/(.*{ <-- HERE 41}
+)$/ a

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    Which tells you that your regex should be 

    /(.{41})$/

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    Note the absence of '*'.

    Alternatively, you could also use 

    $last_41 = substr $buffer, -41;

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    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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Re: Regex to match last n characters of a string
by Zaxo (Archbishop) on May 13, 2005 at 06:21 UTC

    You have an error in the regex; too many quantifiers - drop the asterisk, ($last_41) = $buffer =~ /(.{41})$/; You could also do this with substr, $last_41 = substr $buffer, -41;

    After Compline,
    Zaxo

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Re: Regex to match last n characters of a string
by gopalr (Priest) on May 13, 2005 at 06:25 UTC

    Remove the asteric(*) and run it.

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Re: Regex to match last n characters of a string
by displeaser (Hermit) on May 13, 2005 at 06:34 UTC
    Hi,
    after using diagnositics I get the following:

    (F) You can't quantify a quantifier without intervening parentheses. So things like ** or +* or ?* are illegal. The <-- HERE shows in the regular expression about where the problem was discovered. This should work:

    use strict;
    use warnings;
    use diagnostics;
    my $last_41;
    my $buffer="a"x50;
    ($last_41)= $buffer =~ /(.*){41}$/;


    Hope this helps some
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Re: Regex to match last n characters of a string
by displeaser (Hermit) on May 13, 2005 at 07:06 UTC
    oops,sorry about that

    I should have looked at this a little better,

    use strict;
    use warnings;
    use diagnostics;
    my $buffer="a"x50;
    $buffer =~ /(.{41})$/;
    print $1;


    now this actually works.
    The perl "Perlre" doc has the answer (in a better way then i can phrase it. I think that the curly bracket was been interpretted as a normal character and not a quantifier.
    again sorry for original post.
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