Hi

use strict;
use warnings;

my @outer = (qw| one two three |);

print "First\n";
foreach my $o (@outer) {
    print $o, "\n";
}

print "Second\n";
foreach my $o (@outer) {
    $o .= 'HIII';
    print $o, "\n";
}

print "ARRAY " , @outer , "\n";

#print $o, "\n"; # Comment out compile time error
print "Third\n";
foreach my $o (@outer) {
    print $o, "\n";
}
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Output :-

First
one
two
three
Second
oneHIII
twoHIII
threeHIII
ARRAY oneHIIItwoHIIIthreeHIII
Third
oneHIII
twoHIII
threeHIII
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This is just to make you clear on what had happened in the following loop:-

foreach my $o (@outer) {
    $o .= 'HIII';
    print $o, "\n";
}
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The above loop actually modifies the value in the Memory region where it is pointing to. $o points the memory region of all indexes of array. so It modifies the element of array.