why perl's if condition is satisfying empty string?

The below code works fine, except for the part the STDIN takes an empty value also and goes to first selection "print "Selected Y \n";". If I use && $check ne "" ) { after /^[Y]?$/i, the issue with empty STDIN also solves. But the question is why empty value passes there? my $check = 'NULL'; while ( $check eq 'NULL' ) { print "Do you wish to continue? (Y/N)\n\n"; print "Enter Selection: "; chomp ( $check = ); if ( $check =~ /^[Y]?$/i ) { print "Selected Y \n"; } elsif ( $check =~ /^[N]$/i ) { print "Selected N \n"; } else { print "\nInvalid input, please re-enter selection. (Y/N) \n\n"; $check = 'NULL'; } I am new to perl, can someone help me understand the behavior?