#!/usr/bin/perl -w
use strict;

my @values = (
    15,
    49,
    51,
    79,
);

my $pos = 50;
my $diff;
my @results;

for my $value (@values) {
    if (not defined $diff or abs($pos - $value) < $diff) {
        $diff = abs($pos - $value);
        @results = $value;
    } elsif (abs($pos - $value) == $diff) {
        push @results, $value;
    }
}

print join "\n", @results;