in reply to ambiguous regex match

First, you're using the wrong $data variable. Second, as Corion points out, you need to protect with if.

my $data = 'blabla;tag1=12345;blabla;tag2=99999';

my $tag1;
my $tag2;

$data =~ /tag1=(\d+)/;
$tag1 = $1 if $1;

$data =~ /tag2=(\d+)/;
$tag2 = $1 if $1;

#
# or
#

# the '?' in the below regex means it'll grab the closest
# tag2, and ignore any beyond it

($tag1, $tag2)
  = $data =~ /tag1=(\d+).*?tag2=(\d+)/ if $1 && $2;

print "$tag1, $tag2";

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Update: I could have sworn you were using $2 in the second match. If that was the case and you edited your post, I want to point out that when doing independent matches, the second run to get a match will re-use $1. To use $2, you need both capture groups within a single regex.

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Re^2: ambiguous regex match
by Laurent_R (Canon) on Jul 24, 2015 at 17:07 UTC 
    $data =~ /tag2=(\d+)/;
$tag2 = $1 if $1;

    [download]
    I am afraid this will not work correctly if the regex fails, because $1 will still be set to its previous value (previous regex match). So that rather than testing $1, we should test whether the regex matched.

    I think that you would need rather something like this: 

    $tag1 = $1 if $data =~ /tag1=(\d+)/;
$tag2 = $1 if $data =~ /tag2=(\d+)/;

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