#!/usr/bin/perl
use strict;
use warnings;
my $foo = shift || 12;
my $i = 1;
print "Is \`$foo' a two-digit number ... ";
my $rc = ($foo =~ /^[0-9]{($i + 1)}$/) ? 'yes' : 'no';
#my $rc = ($foo =~ /^[0-9]{2}$/) ? 'yes' : 'no';
print $rc,"\n";