my %hash = ( var1 => 'value1', var2 => 'value2' );
  # ... or whatever...

while ( $tmpl =~ /@~(.*?)~@/ and exists( $hash{$1} )) {
    my $var = $1;
    $tmpl =~ s/@~$var~@/$hash{$var}/g;
}
croak "Bad template text:\n$tmpl" if ( $tmpl =~ /@~|~@/ );