$ perl -e '$a=inf; print ++$a,"\n"' ing $ perl -v This is perl 5, version 14, subversion 2 (v5.14.2) built for darwin-thread-multi-2level #### $ perl -Mwarnings -e '$a=inf; print ++$a,"\n"' Unquoted string "inf" may clash with future reserved word at -e line 1. ing $ perl -Mstrict -e '$a=inf; print ++$a,"\n"' Bareword "inf" not allowed while "strict subs" in use at -e line 1. Execution of -e aborted due to compilation errors.