If you don't want to parse the email address yourself, visit CPAN and fetch Net::ParseWhois.

#!/usr/bin/perl -w

use strict;
use Net::ParseWhois; # also see Net::Whois

my $dom = 'domain.com';
my $w   = Net::ParseWhois::Domain->new($dom);

unless ($w->ok) {
  warn "error: " . $w->{'error'} . "\n" if $w->{'error'};
  die "No whois match for $dom\n";
}

my $c = $w->contacts;

# or BILLING or TECHNICAL
my $email = (split / / => $c->{ADMINISTRATIVE}[0])[-1];

unless ( index( $email, '@' ) > -1 ) {
  ($email = $c->{ADMINISTRATIVE}[-1]) =~ s/^Email: //;
}

print "administrative email address: $email\n";
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--sacked