Most likely, the PATH system variable has not been populated by the path of perl.exe. Go to command prompt, go to the directory where your perl is installed, for example if you installed in C:\Perl, then go to C:\Perl\bin and then type perl -v
you can further test by executing your hello world program by typing
Code:
c:\Perl/bin>perl c:\perl_scripts\hello.pl
i.e., calling the perl program from within the bin directory