I think the actual regex question has been dealt with. Here a couple of additional tips that I find useful when dealing with regex:

1) Assign directly to a variable without using $1. The list on the left can be expanded, especially useful when there is $2,$3, etc. I prefer to get a meaningful name ASAP.

my ($first) = string =~ /some regex with capture/;
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2) Often the //= operator is useful:

$first //= '';
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Assigns $first to the null string if it is undefined. Introduced I think in Perl 5.10. You have something that evaluates to false, yet can be printed without an error.