The easiest approach is to traverse your list of locations and compute the distaance of each location from your designated position. To get locations of zip codes, try Geo::Coder::US:

use Geo::Coder::US;
Geo::Coder::US->set_db( "geocoder.db" );
my ($ora) = Geo::Coder::US->geocode(
                    "1005 Gravenstein Hwy N, 95472" );
print "O'Reilly is located at $ora->{lat} degrees north, "
                             "$ora->{long} degrees east.\n";
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To compute distances, use Geo::Ellipsoid:

use Geo::Ellipsoid;
  $geo = Geo::Ellipsoid->new(ellipsoid=>'NAD27', units=>'degrees');
  @origin = ( 37.619002, -122.374843 );    # SFO
  @dest = ( 33.942536, -118.408074 );      # LAX
  ( $range, $bearing ) = $geo->to( @origin, @dest );
  ($lat,$lon) = $geo->at( @origin, 45.0, 2000 );
  ( $x, $y ) = $geo->displacement( @origin, $lat, $lon );
  @pos = $geo->location( $lat, $lon, $x, $y );
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