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";