If you're using the CGI.pm shortcuts (and why shouldn't you?), you can set the default value using the param method:

use CGI qw/:all/;

...

my $previous_value = "This is what I wrote before"; # fetch this someh
+ow
param('story', $previous_value); # sets default to previous
...
print textarea('story'); # prints an input form element, defaulting to
+ previous value for  it
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