You can use regex quoting to build up expressions from pieces. It looks something like this:

my $name = qr/\w{1,100}/;
my $num  = qr/\d{1,100}/;

$input =~ m{
   employee
   \(
   ($name)
   ,\s*
   ($name)
   ,\s*
   ($num)
   \)
   }x;
my ($first_name, $last_name, $number) = ($1, $2, $3);
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So you can store regexes in vars usin the qr quoting operator, then use them in subsequent regexes merely by mentioning them. They will interpolate.
Phil