cgi.pl

use strict;
use MyMod;

my %hash = ( usual=>'stuff',so=>'on',foo=>'bar' );
%hash = MyMod->do_stuff(%hash);
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MyMod.pm

package MyMod;
use strict;

sub do_stuff
{
  shift;
  my %newhash=@_;
  #stuff
  return %newhash;
}
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