You can use param() to change or set the value of a form field. Here is an example:

#!/usr/local/bin/perl -w
use CGI qw(:standard); 
param("foo","You can\nMake it multiline\noutput too");
print header; 
print start_html(-title=>"Spellchecker", -BGCOLOR=>"black"); 
print hr; 
print start_form; 
print p(submit("Check Spelling"), textfield("hold")); 
print textarea(-name=>'foo', -rows=>10, -columns=>36); 
print end_form;
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