Im quite new to Perl so I'm having a little bit of difficulties in trying to understand this code below. If someone can explain by adding comment to each of the lines it would be very helpful. Starting from the push @gates. Thanks!

#!/usr/bin/perl  
 #levelization.plx  
 use warnings;  
 use Data::Dumper;  
 use strict;  
 my $bench_file = $ARGV[0];  
 my $file_name;  
 my $circuit_name;  
 my $element;  
 my @input_array;  
 my @output_array;  
 my @wire_array;  
 my @gates;  
 my @sorted_gates;  
 my @wire_struct;  
 my @input_list_struct;  
 my @gate_queue;  
 #my @fanout_test;  
 my $num_inputs=0;  
 my $num_outputs=0;  
 my $num_wires=0;  
 my $num_gates=0;  
 my $gate_name_temp;  
 my $gate;  
 my $line;  
 my $role;  
 my $inp;  
 my $inp_test;  
 #Test netlist file  
 if($bench_file =~ /(.*).v/)  
 {  
 $file_name = $1;  
 }   
 else  
 {  
 print "Format of bench file name: circuit_name.v \n example : s1423.v
+\n";  
 }  
 #Read Netlist File  
 while(<>)  
 {  
   my $INPUT_DATA = $_;  
   chomp($INPUT_DATA);  
 {  
 #MODULE NAME  
 if($INPUT_DATA =~ /module (\w+) /)  
 {  
   $circuit_name = $1;  
   print "circuit name = $circuit_name\n";  
 }  
 #INPUT OUTPUT WIRES  
 if($INPUT_DATA =~ /input (.*);/)  
 {  
   @input_array = split /,/, $1;  
 }  
 if($INPUT_DATA =~ /output (.*);/)  
 {  
   @output_array = split /,/, $1;  
 }  
 if($INPUT_DATA =~ /wire (.*);/)  
 {  
   @wire_array = split /,/, $1;  
 }  
 my @wire1;  
 my @wire2;  
 my @wire3;  
 my $gate_name_temp;  
 my $gate;  
 my $line;  
 my $role;  
 #AND, OR, NAND, NOR, XOR  
 if(($INPUT_DATA =~ /(.*) (.*) \((.*),(.*),(.*)\);/) && ($INPUT_DATA !
+~ /module/))
 {  
   push @gates,   
   {   
      num_inputs => 2,  
      gate_type => "$1",   
      gate_name => "$2",   
      output =>   
      {  
        wire_name => "$3",  
        sa0 => 1,  
        sa1 => 1,  
        level => 0,  
      },  
      input_1 =>   
      {  
        wire_name => "$2_$4",   
        CC0 => 1,  
        CC1 => 1,  
        level => 0,  
      },  
      input_2 =>   
      {  
        wire_name => "$2_$5",   
        CC0 => 1,  
        CC1 => 1,  
        level => 0,  
      },  
      processed => 0,   
      processed_ip1 => 0,  
      processed_ip2 => 0,  
      gate_level => -1,  
      shifted => 0  
   };  
 }  
 #INV, BUF  
 #DE - Doesnt Exist  
 #renaming the gates at inputs of the gates for fanouts  
 if($INPUT_DATA =~ /(INVX1|BUFX1) (.*) \((.*),(.*),(.*)\);$/) 
 {  
   $gate_name_temp = $2;  
   push @gates,   
   {   
      num_inputs => 1,  
      gate_type => "$1",   
      gate_name => "$2",   
      output =>   
      {  
        wire_name => "$3",  
        sa0 => 1,  
        sa1 => 1,  
        level => 0,  
      },  
      input_1 =>   
      {  
        wire_name => "$2_$4",   
        sa0 => 1,  
        sa1 => 1,  
        level => 0,  
      },  
      processed => 0,   
      processed_ip1 => 0,  
      gate_level => -1,  
      shifted => 0  
   };  
 }  
 }  
 }  
 #File Read complete  
 #wire struct holds fault data for all wires  
 #input_list_struct is used for levelization  
 for $element (@input_array){  
   print "input: $element\n";  
   push @wire_struct, { wire_name => "$element", sa0 => 1, sa1 =>1, le
+vel => 0};  
   push @input_list_struct, {wire_name => "$element", sa0 => 1, sa1 =>
+ 1, level => 0};  
 }  
 for $element (@wire_array){  
   push @wire_struct, { wire_name => "$element", sa0 => 1, sa1 =>1, le
+vel => -1};  
 }  
 for $element (@output_array){  
   push @wire_struct, { wire_name => "$element", sa0 => 1, sa1 =>1, le
+vel => -1};  
 }  
 print "Initial inputs\n";  
 for my $href ( @input_list_struct ) {  
   print "{ ";  
   for my $role ( keys %$href ) {  
   print "$role=$href->{$role} ";  
 }  
 print "}\n";  
 }  
 $num_gates = scalar @gates;  
 my $index=0;  
 #gate_processed = 2 then all inputs are processed  
 #shift gate into the queue if even one of the inputs processed  
 while($num_gates != 0)  
 {  
   for my $gate(@gates){    
      for my $inp (@input_list_struct){  
        my $inp_test = $inp->{wire_name};  
        if(($gate->{input_1})->{wire_name} =~ m/$inp_test$/){  
           $gate->{processed_ip1} = 1;  
           if($gate->{num_inputs}==1){  
             print "NOTE: $gate->{gate_name}:$gate->{processed}\n";  
             getc();  
             if($gate->{processed}!=$gate->{num_inputs}){  
                unshift(@gate_queue,$gate);  
             }  
           }  
           elsif($gate->{processed_ip2}==1){  
             $gate->{processed}=$gate->{num_inputs};  
           }  
           elsif($gate->{processed}!=$gate->{num_inputs}){  
             if($gate->{shifted}==0){  
                print "1. shifting $gate->{gate_name} to gate queue\n"
+;  
                getc();  
                unshift(@gate_queue,$gate);       
             }  
           }  
        }  
        if(($gate->{num_inputs}!=1)){  
           if(($gate->{input_2})->{wire_name} =~ m/$inp_test$/){  
             $gate->{processed_ip2} = 1;    
             if($gate->{processed_ip1}==1){  
                $gate->{processed}=$gate->{num_inputs};  
             }  
             if($gate->{processed}!=$gate->{num_inputs}){  
                if($gate->{shifted}==0){  
                  print "2. shifting $gate->{gate_name} to gate queue\
+n";  
                  getc();  
                  unshift(@gate_queue,$gate);  
                }  
             }  
           }  
        }  
      }  
   }    
   print "Gates in gate queue\n";  
   for my $line (@gate_queue)   
   {  
      for my $role (keys %$line)  
      {  
        if($role =~ m/^input_1$/)  
        {  
           print "$role: $line->{$role}->{wire_name},";  
           print "lvl: $line->{$role}->{level},";  
        }  
        elsif($role =~ m/^input_2$/)  
        {  
           print "$role: $line->{$role}->{wire_name},";  
           print "lvl: $line->{$role}->{level},";  
        }  
        elsif($role =~ m/^output$/)  
        {  
           print "$role: $line->{$role}->{wire_name},";  
           print "lvl: $line->{$role}->{level},";  
        }  
        else  
        {  
           print "$role:$line->{$role},";  
        }  
      }  
      print "\n";  
   }  
   getc();  
 #if both inputs of the gates are processed, then calculate the level 
+of the gate  
 #if only one of the inputs are processed, then add the gate to the en
+d  
   my $num_gate_queue = scalar @gate_queue;  
   while ($num_gate_queue != 0)  
   {  
      $gate = pop(@gate_queue);  
      if($gate->{num_inputs}==1){  
        print "Number of gates in queue: $num_gate_queue";  
        if($gate->{processed_ip1}==1){  
           $gate->{processed}=$gate->{num_inputs};  
        }  
      }  
      if($gate->{processed}==$gate->{num_inputs}){  
        if($gate->{num_inputs}==2){  
           if(($gate->{input_1}->{level})>($gate->{input_2}->{level}))
+{  
             $gate->{gate_level} = ($gate->{input_1}->{level});  
           }  
           else{  
             $gate->{gate_level} = ($gate->{input_2}->{level});  
           }  
           $gate->{gate_level}++;  
           $gate->{output}->{level}=$gate->{gate_level};  
           unshift(@input_list_struct,$gate->{output});  
           $num_gate_queue--;  
           $num_gates--;  
           print "Number of gates left $num_gates";  
           getc();    
        }  
        elsif($gate->{num_inputs}==1){  
           print "input level: $gate->{input_1}->{level}\n";  
           getc();  
           $gate->{gate_level} = $gate->{input_1}->{level};  
           $gate->{gate_level}++;  
           $gate->{output}->{level}=$gate->{gate_level};  
           print "$gate->{gate_name}: $gate->{gate_level}";  
           unshift(@input_list_struct,$gate->{output});  
           $num_gate_queue--;  
           $num_gates--;  
           print "Number of gates left $num_gates";  
           getc();    
        }  
      }  
      else{  
 #       if($gate->{shifted}==0){  
        print "3. shifting $gate->{gate_name} to gate queue\n";  
        getc();  
        unshift(@gate_queue,$gate);  
        $num_gate_queue--;  
 #gates that are not processed because of lack of second input being p
+rocessed are shifted in here, they need not be shifted again  
        $gate->{shifted}=1;  
 #       }         
      }  
   }  
   print "updated input list\n";  
   for my $href ( @input_list_struct ) {  
      print "{ ";  
      for my $role ( keys %$href ) {  
        print "$role=$href->{$role} ";  
      }  
      print "}\n";  
   }  
 #the updated levels of the wires are present in input_list_struct  
 #update the fanouts of the gate with the levels from this struct  
   print "modifying gate: level input of gate\n";  
   for $gate(@gates){    
      for $inp (@input_list_struct){  
        $inp_test = $inp->{wire_name};  
        if(($gate->{input_1})->{wire_name} =~ m/$inp_test$/){   
           $gate->{input_1}->{level} = $inp->{level};  
           print "$gate->{gate_name}: $gate->{input_1}->{wire_name} - 
+$gate->{input_1}->{level}\n";  
        }  
        if($gate->{num_inputs}!=1){  
           if(($gate->{input_2})->{wire_name} =~ m/$inp_test$/){   
             $gate->{input_2}->{level} = $inp->{level};  
           }  
        }  
      }  
   }  
 }  
 print "gate: level\n";  
 for $gate (@gates){  
   print "$gate->{gate_name}: $gate->{gate_level}\n";  
 }

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