So what kinds of things go into $FindWhat and how is that different than @Column's hashes? Why don't you try out Text::Template? It already does this stuff and without having to invent your own parser.

If all else fails, you could track what $-[0] and $+[0] are when you copy $1 and later use substr() to write back to $Template at those offsets with your replacement.

I don't buy your argument about not using s/// on the grounds that it appears you're rejecting it on some faulty assumptions. Regardless, here's a s///ge alike without actually using s///.

# Ala
my $region_start = $-[0];
my $region_length = $+[0] - $-[0];
my $OriginalLine = $1;
...

substr $Template, $region_start, $region_length, $ReplacementString;
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