counter for each regex match.

tty1x has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to increase the $count variable by 1 whenever any line in the opened file contains the word Mailto:

However, I kept receiving use of uninitialised value $count error and a long string of numbers at the end as the result.

my @email = <OPENFILE>;
close OPENFILE;

my $count;

foreach my $email (@email){

    if ($email =~ /mailto:/) {
    $count += 1;

    }

    print $count; # error here
}
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Comment on counter for each regex match. Download Code

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Re: counter for each regex match. by davido (Cardinal) on May 04, 2013 at 06:05 UTC
`$count`'s initial state is "undef", or undefined. It doesn't get incremented until the first time that "mailto:" shows up in your input file. Yet you print its value on each iteration. So imagine the first line of your file is, "`More pizza please!`". The regex obviously won't match, and so `$count` won't be incremented. So when you print $count's value, it is still 'undef'. Either initialize it with a value right where you're declaring $count, or move it outside of the foreach loop, or put an "`if defined $count`" suffix at the end of your print statement. Dave	[reply] [d/l] [select]
Re^2: counter for each regex match. by tty1x (Novice) on May 04, 2013 at 12:51 UTC
Thanks for the explanation. Moving the print statement out of the for loop did the trick. Elementary mistake =/	[reply]
Re: counter for each regex match. by Laurent_R (Canon) on May 04, 2013 at 08:16 UTC
However, I kept receiving use of uninitialized value $count error and a long string of numbers at the end as the result. From your own description of the problem, the main point is to move the print statement outside of the while loop, so that it gets executed only once after you have finished looping on the input. Initializing $count to 0 when you declare it is slightly less important, but it will avoid the "uninitialized value" warning in the case where nothing was matched in your while loop.	[reply]
Re: counter for each regex match. by kcott (Archbishop) on May 04, 2013 at 10:45 UTC
G'day tty1x, Changing `my $count;` to `my $count = 0;` should fix your "uninitialised value" problems. [Aside: you can write `++$count;` instead of `$count += 1;`] -- Ken	[reply] [d/l] [select]
Re^2: counter for each regex match. by tty1x (Novice) on May 04, 2013 at 12:53 UTC
Thanks for the `++$count;` tip :)	[reply] [d/l]