Try the Date::Manip module:

use Date::Manip::Date; 
my $base = Date::Manip::Date->new; 
for my $deltastr ("32:05", "11:32:05") { 
   $delta = $base->new_delta($deltastr); 
   $deltasec = $delta->printf("%sys"); 
   print "$deltastr => $deltasec s\n"; 
}

=begin output

32:05 => 1925 s
11:32:05 => 41525 s

=end output

=cut
[download]

Update: this is incorrect, for it doesn't work for times greater than a day that ps outputs, eg. "35-04:04:09". I guess there's no simpler workaround other than separating the fields (or at least the day field) manually using a regex.