Error using Perforce within Emacs

I've obtained p4.el and put the following in my .emacs, running under cygwin:

(setq p4-executable "p4")
(load-library "p4")

p4.exe is the cygwin version.

On running M-x p4-info I get the following error:

/path/to/p4.exe: error while loading shared libraries: ?: cannot open shared object file: No such file or directory

Yet running M-! p4 info works fine. Probably I'm missing an en开发者_StackOverflow社区v variable. Apologies if this is a basic question - I'm new to emacs.

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Try adding (p4-set-p4-executable "/my/path/to/p4") to your .emacs.