added a simple infix arithmetic calculator.
added a simple infix arithmetic calculator.

stmuk/perl6-examples,Quinny/perl6-examples,stmuk/perl6-examples,Quinny/perl6-examples,shlomif/perl6-examples,stmuk/perl6-examples,shlomif/perl6-examples,Quinny/perl6-examples,Quinny/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,Quinny/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples