Single dash phone number - regex validation

Question

I need a simple regex to validate a phone number of the form x-y, where x and y can represent any number of digits and the dash is optional, but if it does show up it most be within the string (the dash must have digits at its left and right)

Answer 1

/^\d+(?:-\d+)?$/ should do the trick.

Answer 2

/^\d+(-\d+)?$/) seems to work. It matches one or more leading digits, with an optional "hyphen followed by one or more digits".

#!/usr/bin/perl
#
@A = ( "1-2",
       "-12",
       "12-",
       "123-1234",
       "1-",
       "-1",
       "123",
       "1",
       "foo-bar",
       "12foo34",
       "foo12-34",
       "12f-o34",
       );

foreach (@A) {
  if (/^\d+(-\d+)?$/) {
    print "\"$_\" is a phone number\n";
  } else{
    print "\"$_\" is NOT a phone number\n";
  }
}

gives:

$ ./phone.pl 
"1-2" is a phone number
"-12" is NOT a phone number
"12-" is NOT a phone number
"123-1234" is a phone number
"1-" is NOT a phone number
"-1" is NOT a phone number
"123" is a phone number
"1" is a phone number
"foo-bar" is NOT a phone number
"12foo34" is NOT a phone number
"foo12-34" is NOT a phone number
"12f-o34" is NOT a phone number