True, unless you get rid of the while entirely. The first paragraph of s/// documentation reads: (Emphasis mine)

Searches a string for a pattern, and if found, replaces that pattern with the replacement text and returns the number of substitutions made.

So you get

my $post_body = ...from db...;
my $match = s/.../.../ig;
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By the way, I don't think $match should be singular. $matches is better but not nearly as descriptive as something like $num_blks.