$clocks{$pin_name}{'period'} = $Worksheet->{Cells}[$row][$clock_col]->Value;
#snip

foreach my $key (sort keys %clocks){
  print_clock_assertions($clocks{$key},$key);
}

sub print_clock_assertions {
  my($hashref)=$_[0];
  my($clock_name)=$_[1];
  if($hashref->{'virtual'} eq "VIR") {

etc...