DB<106> $tmpl = '$#abc#=15' 
 => "\$#abc#=15"

  DB<107> $placeholder{abc}='str'
 => "str"

  DB<108> $tmpl =~ s/#(\w+)#/$placeholder{$1}/g
 => 1

  DB<109> $tmpl
 => "\$str=15"

  DB<110> eval $tmpl
 => 15

  DB<111> $str
 => 15