I've just re-invented a wheel and discovered a way to say which modules uses given one, and from which location they come.
Quite simple and usefull (for me at least).
for Win32:
perl -Mvars -we "print join qq/\n/,map {qq/$_=>$INC{$_}/} sort keys %I +NC"
for other systems (including Cygwin):
perl -Mvars -we 'print join qq/\n/,map {qq/$_=>$INC{$_}/} sort keys %I +NC'
Sample output will be>D:/perl561/lib/>D:/perl561/lib/>D:/perl561/lib/>D:/perl561/lib/>D:/perl561/lib/ warnings/>D:/perl561/lib/warnings/
If other module needed, specify, for example, other -M option