#! perl -slw
use strict;

my $re = qr[^\d{3}-\d{3}$];
my $pat = '111-111';

my @inputs = (
	'',
	'a',
	'1',
	'12',
	'12x',
	'123',
	'1234',
	'123-',
	'123x',
	'123-4',
	'123-x',
	'123-456',
	'123-4567'
);

for my $input ( @inputs ) {
	print "$input failed" and next if length $input > length $pat;
	my $test = $input . substr( $pat, length( $input ) );
	print $input, $test =~ $re ? ' passed' : ' failed';
}

__END__
P:\test>471541
 passed
a failed
1 passed
12 passed
12x failed
123 passed
1234 failed
123- passed
123x failed
123-4 passed
123-x failed
123-456 passed
123-4567 failed