Hi there,
Thanks to you both for the quick response. yes, the $output variable was a typo. As for the naming convention, I got that from an exceprt in "Win32 Perl Programming", here's the code again:

#!usr/bin/perl

use Win32::API;

my $filename="C:/Program Files/America Online 9.0g/aol.exe";

my $apiobject = new Win32::API("C:/Documents and Settings/Mdaviesie/De
+sktop/dver_1.3/fileversion.dll", "GetFileVersionTxt", 'PP','I') or di
+e "Failed to acquire API: $^E";

#Set some memory aside for the returned value
my $string="\x00" x 1024;

#Call the function in the dll
$apiobject->Call($filename,$string);

#Remove the unused padding in the string
my $final = ($string =~/(.*?)\x00/);

print "\$final - $final";
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A bit of background, all the dll is supposed to return is the version number of the named file. The function I want to call looks like this:

INT GetFileVersionTxt(STRING sFile, out STRING sVersion)
[download]

The dll returns a version number (I was using the fileversion modules before, but their output is slightly different to what this dll returns - which is why I have to try to work with it). If anybody could provide me with a pointer as to why this is returning the error message,
Thanks again,
Jonathan