After I run Makefile.PL, it showd this message.

Failed to find iconv, please check your settings and re-run as:
/usr/bin/perl Makefile.PL LIBS='-L/path/to/lib' INC='-I/path/to/include'

I have iconv installed in /usr/bin/iconv.
What should I do to make the module works?
Any advice would be very appreciated,
thank you very much in advance.