qr{(?\QNAS-IP-Address=\E)} ##

##

(?-xism:(?NAS\-IP\-Address\=))

##

##

chomp( my $pat =  );

while () {
   print if /$pat/;
}

__DATA__
(?-xism:(?NAS\-IP\-Address\=))
...

##

##

chomp( my $pat =  );
my $re = qr/$pat/;

while () {
   print if /$re/;
}

__DATA__
(?-xism:(?NAS\-IP\-Address\=))
...