Everybody explained why map doesn't mix too well with s/// and how you want a different delimiter than the forward slash there, but what I wonder is why you're using map at that point at all? It would be far simpler to say

while (my @row = $sth->fetchrow_array()) {
    s!$term!"<i>$term</i>"! for @row;
    # ...
}
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You also probably want to escape pattern metacharacters in $term (s!\Q$term!"<i>$term</i>"!, perldoc -f quotemeta), and it might help to precompile the pattern:

my $rx = qr/\Q$term/;
while (my @row = $sth->fetchrow_array()) {
    s!$rx!"<i>$term</i>"! for @row;
    # ...
}
[download]

Makeshifts last the longest.