for ($etime){
  my ($dd,$hh,$mm,$ss)=()
  # see man ps etime looks like [[dd-]hh:]mm:ss
  if ( /^(?:(?:(\d{1,2})-){0,1})(?:(?:(\d{2}):){0,1})(\d{1,2}):(\d{2})$/
){
    $dd = $1 || ''; $hh = $2 || ''; $mm = $3; $ss = $4;
    $etime_secs= $ss+($mm*60)+($hh*60*60)+($dd*24*60*60);
  }
}

##</code><code>##

for ($etime){
  # see man ps etime looks like [[dd-]hh:]mm:ss
  # if either $dd and $hh are not present then they will eat 
  # up the $mm & $ss so split on a non digit and reverse it:
  my ($ss, $mm, $hh, $dd)= reverse split /\D/;
  $hh += 0;   # stop warning as $hh may not be initialised
  $dd += 0;   # same as $hh :)
  $etime_secs= $ss+($mm*60)+($hh*60*60)+($dd*24*60*60);
}