use List::Util 'reduce';

  my $closest = reduce { abs($a - $ctime) < abs($b - $ctime) ? $a : $b } @epochs;
  print $closest;

##</code><code>##

  my $closest = reduce { $a->[1] < $b->[1] ? $a : $b }
                map [ $_ => abs($ctime - $_) ], @epochs;
  print $closest->[0];