Perl while loop won't exit when blank line is entered - arrays

Question

I am trying to print the sum, maximum, and minimum values of list of numbers but I am struggling to get it working.
When I press Enter the loop should exit but the program keeps running
use strict;
use warnings;
my #items;
my ( $sum, $max, $min );
while ( chomp( my $num = <STDIN> ) ) {
last if ( $num eq '\n' );
$max ||= $num;
$min ||= $num;
$sum += $num;
$max = $num if ( $num > $max );
$min = $num if ( $num < $min );
push( #items, $num );
}
printf( "Entered numbers are: %s \n", join( ', ', #items ) );
print( "Sum of all numbers is : ", $sum );
print "\n";
print( "Minimum number is : ", $min );
print "\n";
print( "Maximum number is : ", $max )

Answer 1

You can't use chomp inside a while condition like this
while (chomp(my $num = <STDIN>)) { ... }
because the while loop needs to terminate when the <> returns undef at end of file. So you must put the chomp as the first statement of the loop
The simplest way to exit a loop like this is to check whether the input contains any non-space characters using the regular expression /\S/
The check
last if ( $num eq '\n' )
won't work because you have used chomp to remove the newline from the input. Also, if you use single quotes '\n' is the two-character string \ followed by n. You need double quotes like "\n" to create a newline
When a scalar variable is first declared it has the value undef, so you can avoid any clumsy initialisation by testing for this and updating $min and $max unless the previous value is already defined and higher (or lower) than the new value
I would rewrite your program like this.
use strict;
use warnings;
my #items;
my ($sum, $max, $min);
while (my $num = <STDIN>) {
chomp $num;
last unless $num =~ /\S/;
$max = $num unless defined $max and $max >= $num;
$min = $num unless defined $min and $min <= $num;
$sum += $num;
push #items, $num;
}
print 'Entered numbers are: ', join(', ', #items), "\n";
print "Sum of all numbers is: $sum\n";
print "Minimum number is: $min\n";
print "Maximum number is: $max\n";

Answer 2

If you want to detect Enter, you can't chomp the input before. Also, '\n' is not the enter, you have to use double quotes "\n" to enable special characters.
The while (<>) loop is usually ended by Ctrl+D.
Moreover, you can find a module to do the work for you.
#!/usr/bin/perl
use warnings;
use strict;
use List::Util qw{ max min sum };
my #items = <>;
chomp #items;
my $max = max(#items);
my $min = min(#items);
my $sum = sum(#items);
print "Entered numbers are: #items\n";
print "Sum of all numbers is: $sum\n";
print "Minimum number is: $min\n";
print "Maximum number is: $max";