You want the LIKE function.:

my $sql = 'SELECT *
            FROM clttable
            WHERE clt LIKE ?';
my $sth = $dbi->prepare $sql;
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LIKE patterns are simple, _ is wild for a single character, % matches any number including none.

I set this up with a placeholder so you don't need to prepare each query.

Update Oops, mixed patterns with shell in my head, repaired.

After Compline,
Zaxo