There's also s///e (as used in Template::Tiny):

# load values into %config, template into $string, then...
1 while $string =~ s/\[%\s*(\S+)\s*%\]/$config{$1}/;
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or just plain old string interpolation:

# load values into e.g. $CONFIG::variable1, etc., then...
$string = eval "package CONFIG;\n<<END_TEMPLATE;\n".$string."\nEND_TEM
+PLATE\n";
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Basically, if you just have to substitute in some variables, it's not worth using a fancy framework. If you have to do more, you won't find any module to help you in core Perl.