export variable outside foreach

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

Hi guys,

Am pretty new to perl and wanted to export the last value of $last. But it doesn't work. Could you help?

ps: I just wanted to make the equivalent of a Unix "tail -1"

use CGI qw(:standard);
use strict;
use utf8;

my $srce = "/some/file";
my $string1 = "some-regex";
my $last;

open my $fh, $srce or die "Could not open $scre: $!";

my @lines = grep /\Q$string1/, <$fh>;
foreach my $line (@lines) {
    my @fields = split /\s+/, $line;
    $last= $fields[3];
}
print "$last";
[download]

thanks

Comment on export variable outside foreach Download Code

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Re: export variable outside foreach by Eily (Monsignor) on Jun 19, 2014 at 08:38 UTC
What do you mean by "it doesn't work" ? Does it print something wrong, or nothing at all? See How do I post a question effectively? Since you have replaced your values and have not given any sample data, I can't tell if this is on purpose but in `/\Q$string1/` $string1 is interpreted as a literal string, not a regular expression. This means for example that "a" will match "ab+c" and not "aaaaaaa". To have your string interpreted as a regex, do not use \Q	[reply] [d/l]
Re: export variable outside foreach by Anonymous Monk on Jun 19, 2014 at 08:29 UTC
sure it does ... if $last is empty then @fields was empty or @lines is empty	[reply]
Re^2: export variable outside foreach by mitchreward (Acolyte) on Jun 19, 2014 at 08:34 UTC
perl -w test.pl Global symbol "$scre" requires explicit package name at test.pl line 12. Execution of test.pl aborted due to compilation errors.	[reply]
Re^3: export variable outside foreach by Anonymous Monk on Jun 19, 2014 at 08:47 UTC
Is that a question? :D Fix your typo, copy the varible name, ctrl+f, paste variable name, enter, find the typo, fix it	[reply]
Re^3: export variable outside foreach by roboticus (Chancellor) on Jun 19, 2014 at 13:01 UTC
mitchreward: He meant that $srce is not the same as $scre. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re^2: export variable outside foreach by Eily (Monsignor) on Jun 19, 2014 at 08:43 UTC
@lines being empty seems unlikely, since it was grepped out of the file. @fields may not contain four fields though (Edit: whoops, @lines, can be empty, is just can't contain empty strings unless $string1 is empty) mitchreward, have a look at Data::Dumper. If you `use Data::Dumper;` and then add `print Dumper \@fields;` to your loop you may have more information on what is happening. Edit: the code you provided does compile, so you have removed the error by changing it.	[reply] [d/l] [select]
Re^3: export variable outside foreach by AnomalousMonk (Archbishop) on Jun 19, 2014 at 09:10 UTC
@lines being empty seems unlikely, since it was grepped out of the file. I don't understand this point. Why would `grep`-ing the contents of the file make it likely that the `@lines` array must contain something? (Or does this refer to a previous version of the posted code that was changed without citation?)	[reply] [d/l] [select]
Re^4: export variable outside foreach by Eily (Monsignor) on Jun 19, 2014 at 09:18 UTC
Re: export variable outside foreach by philipbailey (Curate) on Jun 19, 2014 at 15:36 UTC
Perhaps your input file has a final line consisting of a newline only, or line that has no fourth field? That would give the behaviour you describe.	[reply]