Since substr returns an lvalue when less than four arguments are provided, you can do substitutions on portions of the string.

my $str = 'abracadabra';
substr($str, 3, 5) =~ s/a/@/g;
print("$str\n");  # abr@c@d@bra

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I realize this is off-topic, but it's a neat trick that's somewhat related.

In reply to Re: Applying a regex to part of a string by ikegami
in thread Applying a regex to part of a string by holdyourhorses

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