Sub Articulo 125.0

 Does anybody know of a macro (package) which allows you to perform
 character substitution/deletion on its argument?   A typical things I'd
 like are to have calls
 [] 
 which would work so that
 \filterspaces {remove the spaces from this}
 \replacespaces {replace the spaces in this}{_}
 would produce
 removethespacesfromthis
 replace_the_spaces_in_this
 even when used inside other macros.