$ perl -le'
my @numbers = ( "+12 34567890", "+23 45678901", "+34 56789012", "+45 6
+7890123", "+56 78901234" );
for my $num ( @numbers ) {
    print $num;
    substr $num, -4, 0, " ";
    print $num;
    }
'
+12 34567890
+12 3456 7890
+23 45678901
+23 4567 8901
+34 56789012
+34 5678 9012
+45 67890123
+45 6789 0123
+56 78901234
+56 7890 1234
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