You need to splice in elements starting from the end to the beginning. Otherwise, you will confuse splice (as new items added to the front invalidates the following indices). (What used to be say, index 4 will get moved up 1 when a new item is added in front).

When you splice in from the end, you leave the preceding indices alone. 

for my $i (reverse 0 .. $#array) {
    if (($i+1) % 3 == 0) {
        splice @array, $i+1, 0, "new item";
    }    
}
use Data::Dumper; print Dumper \@array;

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Ah, I see davido has the better solution - more efficient.

In reply to Re: Adding an new element after every 5th element in array by Cristoforo
in thread Adding an new element after every 5th element in array by dvinay

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