eval is the easiest way to do this, since you don't end up with your own mini-language to parse; just let perl do it. Here's a very primitive command-line example:

% perl -MData::Dumper -nwe 'chomp; 
  ($sub, $rest) = split / +/, $_, 2; 
  eval "$sub($rest)"; print $@ if $@; print "\n) " } 
  BEGIN { sub spew { print Dumper(@_) } print ") "'
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Presumably you'll have more functions defined than that; consider using Term::Readline or similar if this is something that'll be used a lot.

hdp.