Plperlu func with column as param

I have postgres 9.5, and want to use plperlu as lang to get result from curl put My func is: create or replace function langDetect(str text) returns text as $$ use warnings; use strict; my $str = $_; my $output = curl -X PUT --data $str http://localhost:9998/language/string; return($output); $$ language plperlu; When i use: select langDetect('some text'); Everything is ok But: Select langDetect(column) from table limit 1; Returns empty string. Column type is text. Any help will be good!