regex - A tiny template language -

i pass string "partial" sql statement like:

"select %fields% ... %order% %limit%" 

then want replace %fields% either real list of fields (which array) or count(*). likewise replace %order% either order ... (which generate) or empty string , %limit% either limit ... (which generate) or empty string.

i want way prevent these sequences replaced. example may "turn off" replacing if percents doubled: %%fields%% should not replaced list of fields replaced literal %fields%.

note not insist namely on syntax. instead of percent signs may use other escape syntax (for example ${fields} or {{fields}}).

i want easy , (what more important) efficient way this.

note use perl.

maybe, should not invent own template language regexps , use perl module template::tiny? efficient?

#!/usr/bin/perl  use strict; use warnings;  sub myreplace {   ($tmpl, $hash) = @_;    %hash2;   foreach $key (keys %$hash) {     $hash2{"%$key%"} = $hash->{$key};     $hash2{"\\%$key%"} = "%$key%"; # escaped   }    $re_str = "(" . (join '|', map { "\q$_\e" } keys %hash2) . ")";   $tmpl =~ s/$re_str/$hash2{$1}/g;   return $tmpl; }  print myreplace('select %fields% ... %order% %limit%', {fields=>'a, b, c', order=>'order id', limit=>''}), "\n"; print myreplace('select \\%fields% ... %order% \\\\%limit%', {fields=>'a, b, c', order=>'order id', limit=>''}), "\n";