Of course, if you're using arrays, you just need

if ($lines{$_] eq $lines2[$_]) {
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The following will replace the non-matching chars in the string  $str1 with "*" (and leave the matching chars) by converting $str2 to a regex:

$str2 =~ s/./(?:($&)|.)/g;

print map{$_||'*'} $str1 =~ /$str2/
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