For starters, you should be using a placeholder. 
my $all = $dbh->selectall_arrayref(
   "SELECT ID,
           col_1,
           col_2
      FROM table
     WHERE LOWER(col_1) LIKE ?",
    undef,
    "$searching_string%",
);

[download]

Secondly, did you make sure that LOWER() works with non-ascii characters? The documentation for the function reads

"The lower(X) function returns a copy of string X with all ASCII characters converted to lower case. The default built-in lower() function works for ASCII characters only. To do case conversions on non-ASCII characters, load the ICU extension."

Did you load the ICU extension?

Finally, you provided very little information as to what $searching_string contains. Is it decoded text or is encoded text? If it's encoded, which encoding is used? In case there's a bug in DBD::SQLite, it would also be useful to know which how is the string stored internally, UTF8=0 or UTF8=1? A good starting point would be to give the output of 

use Devel::Peek;
Dump($searching_string);

[download]

In reply to Re: sqlite utf lower by ikegami
in thread sqlite utf lower by fanticla

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