(#print "Enter your guess: \n\n > "; ">" in book's script; why?)

Just to provide a prompt for entering a number, ">" can be "%" or any other character for that matter, like you don't want the user to think that the scrip is hanging or something...

Now to return to line 4 like you want just use a label, a label is used in conjunction with goto, so the first segment of your code can be re-written as:

until ($isover) {
     clear_the_screen();
    print "Find the secret number between 1 and 100:  \n\n";
    LABEL:    print "Enter your guess: \n\n % "; #">" #in book's scrip
+t; why?
    chomp($userguess = <STDIN>);

    #following "while" loop added by me in a "challenge"
    while ($userguess !~ /^[+-]?\d+$/ ) { #testing to see whether user
+ entry is a number
       print "\nYour guess must be a number. Try again.  \n\n";
       goto LABEL;
    }
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Notice, I did not use "chomp($userguess = <STDIN>);" in line 11 since the flow would go from 4 four onwards once again...

I'd stress on using the pragmas:

use strict;
use warnings;
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these can be very helpful at ensuring that you don't mistype a variable name and can give you helpful warnings and thus greatly reduce the debugging time..

with $totalguesses, you can't return outside a subroutine, eval statement or do{}, hence using a print statement instead...

("if" loop beginning on line 17, pressing <Enter> after the 3 "elsif" choices returns the code to line 4)

Not entirely correct, what returns the code to line 4 is that the $isover in until(){} is not defined yet and hence this observation...

There's an extensive repetitive writing of certain statements in your code, that warrants taking a look at Perl subroutines which can enhance the logic-flow interpretation of the code..

Update: I did not mention that I pre-assigned $secretnumber with the value of 100....
Here's your code once again with places for you to notice being commented accordingly:

use strict;
use warnings;

my $isover;           #using strict requires variables declaration wit
+h 'my'.
my $totalguesses;
my $reply;

until ($isover) {
    clear_the_screen();
    print "Find the secret number between 1 and 100:  \n\n";
    LABELED:    print "Enter your guess: \n\n % ";    #labeling a posi
+tion
    
    my $userguess;
    chomp($userguess = <STDIN>);

    while ($userguess !~ /^[+-]?\d+$/ ) {
       print "\nYour guess must be a number. Try again.  \n\n";
       goto LABELED;
    }

      $totalguesses++;
      my $secretnumber=100;
      if ($userguess == $secretnumber) {
         clear_the_screen();
         print "You guessed it! Press <Enter> to return to the Main Me
+nu.\n\n";

         chomp($reply = <STDIN>);
         $isover = 1; #Defines $isover hence the evaluation would retu
+rn true
                   #the until(){} block would exit then...
                   
    }elsif ($userguess > 100) {
        print "\nYou chose a number higher than 100.<Enter> to try aga
+in.\n";
        chomp($reply = <STDIN>);

    }elsif ($userguess < $secretnumber) {
        clear_the_screen();
        print "$userguess is too low. Press <Enter> to guess again.\n\
+n";
        chomp($reply = <STDIN>);

   }elsif ($userguess > $secretnumber) {
        clear_the_screen();
        print "$userguess is too high. Press <Enter> to guess again.\n
+\n";
        chomp($reply = <STDIN>);
        }

    }

print "your guesses $totalguesses\n";

sub clear_the_screen{

    }
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Finally, checking the Perl Documentation at the website or through your console is so rewarding so make it your new-year's new habit :).... Best of luck :)