You are looking for the 'filter' parameter to new.

From the documentation:

  my $filter = sub {
     my $text_ref = shift;
     $$text_ref =~ s/!!!ZAP_(.*?)!!!/<TMPL_$1>/g;
   };

   # open zap.tmpl using the above filter
   my $template = HTML::Template->new(
                    filename => 'zap.tmpl',
                    filter => $filter);
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You would then be able to use !!!VAR name="whatever"!!! Personaly though i like something along the lines of:

sub convert {
   my $text_ref = shift;
   $$text_ref =~ s/\[\%=(.*?)\%\]/<TMPL_VAR NAME=$1>/g;
   $$text_ref =~ s/\[\%\/(.*?)\%\]/<\/TMPL_$1>/g;
   $$text_ref =~ s/\[\%(.*?)\%\]/<TMPL_$1>/g;
}
[download]

This lets me to [%=name%] and [%if name%] [%/if%] which i like more than the default.

Edit by castaway - fixed code tags