If you do a pre-increment/decrement, the value is incremented/decremented and then used wherever. In a post-increment/decrement, the value is used first, and then it is incremented/decremented.

my $i;

$i = 0;
print "\nPost-increment: ", $i++, "\nNow equals: ", $i, "\n\n";

$i = 0;
print "\nPre-increment: ", ++$i, "\nNow equals: ", $i, "\n";
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output

Post-increment: 0
Now Equals: 1

Pre-increment: 1
Now Equals: 1
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