I'm an sql noob, this is my first function... How do I go about creating a function 'fiscal_year' which could create output.txt (below)?

desired-output.txt

xbrl=# select fiscal_year,cik,company_name from csv_table limit 10;
 fiscal_year |   cik   |             company_name
-------------+---------+--------------------------------------
 2010  | 1075607 | TC PIPELINES LP
 2011  | 1075607 | TC PIPELINES LP
 2012  | 1075607 | TC PIPELINES LP
 2012  | 1075607 | TC PIPELINES LP
 2010  | 1314054 | BMX Development Corp.
 2011  | 1423974 | Farrallon, Inc
 2011  | 1396536 | INFORMATION SYSTEMS ASSOCIATES, INC.
 2011  | 1314054 | BMX Development Corp.
 2011  | 1029802 | China Fruits Corp
 2011  | 1310893 | BLUESKY SYSTEMS CORP
(10 rows)

error.txt

ERROR:  syntax error at or near "INTO"
LINE 5:     SELECT INTO myYear
                   ^
CONTEXT:  invalid type name "INTO myYear
        IF extract(month from myDate::date) > 6 THEN
            extract(year from myDate::year)
        ELSE
            extract(year from myDate::year)-1
        END IF"

fiscal_year.bad.sql

CREATE FUNCTION fiscal_year(myDate TEXT) RETURNS TEXT AS
$$
BEGIN
    DECLARE myYear INT;
    SELECT INTO myYear
        IF extract(month from myDate::date) > 6 THEN
            extract(year from myDate::year)
        ELSE
            extract(year from myDate::year)-1
        END IF;
    return myYear;
END;
$$
LANGUAGE plpgsql;

output.txt

xbrl=# select filing_date,cik,company_name from csv_table limit 10;
 filing_date |   cik   |             company_name
-------------+---------+--------------------------------------
 04/27/2011  | 1075607 | TC PIPELINES LP
 04/30/2012  | 1075607 | TC PIPELINES LP
 07/30/2012  | 1075607 | TC PIPELINES LP
 10/30/2012  | 1075607 | TC PIPELINES LP
 05/23/2011  | 1314054 | BMX Development Corp.
 08/12/2011  | 1423974 | Farrallon, Inc
 08/15/2011  | 1396536 | INFORMATION SYSTEMS ASSOCIATES, INC.
 08/15/2011  | 1314054 | BMX Development Corp.
 08/17/2011  | 1029802 | China Fruits Corp
 08/18/2011  | 1310893 | BLUESKY SYSTEMS CORP
(10 rows)