Your first guess was close, but you need scalar context. I chose to let $spliced "double" the matched string. (It did require /ee to accomplish this.

use strict;
use warnings;
my $oldline = qr/xyzzy/;
my $spliced =  q/"$1$1"/;
my @array = (
    'xyzzy blah xyzzy moreBLah xyzzy asdfouyXYZZY',
    'blah xyzzy',
);

my $count;

$count +=  s/\b($oldline)\b/$spliced/gee for @array;

$" = "\n";
print "@array\n\n";
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OUTPUT:

xyzzyxyzzy blah xyzzyxyzzy moreBLah xyzzyxyzzy asdfouyXYZZY
blah xyzzyxyzzy

4
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